I want to start another useless Nerd debate.

Saturation/sample rate means you are thinking of analog gear? That is actually a point.

To me a dedicated (digital) board does have a few benefits.

Interactivity (boosting creativity) while playing. This is something generic master keyboards do not match (own a NI Kontrol MK3, in front of the computer).

Well crafted and practical usable set of sounds (bread&butter at least). There are few VSTi of this lineage. Even the standard Kontakt libraries fall short in this respect. VSTi very often are geared towards "the next whow sound effect". Sounds interesting but you realize quickly that it is used rather seldomly.

Complexity of VSTi choices, each being a one-trick-pony. Each having a different UI and concept.

And I challenge the need for the final bit of pristine sound quality (of natural instruments for example). A piano with 90gb samples? Why? Would only make sense as a solo instrument. Otherwise you either do not hear that the pianist farted slightly when playing some notes hard :-) or the sound is actually getting in the way of other instruments in a mix. EQ time.

AT

More is not necessarily better, hence why people look back fondly on past decades like the 70s and 80s where people went into studios and worked with the analog gear available, and pushed the boundaries of that hardware, or embraced the limitations and character of it.

It's a bit like asking why you would want to speak to one person face to face when you could be digitally interacting with multiple people around the world.

It's all down to the individual, and great that we have so many choices, but at the same time music has become a very sterile environment where we're continuously being encouraged to be lazier and seek out products to use as a crutch, whilst having so much poked into our brains via external influences.

If you really want the answer, Try a month with no internet, and only using analog hardware and see how that affects your productivity or output vs a digitally emulated environment. I'm pretty sure that most people would feel far more engaged and focused on their art, without distractions.

What does hardware do better than software emulation?

Switch it on and it's ready to go
Software needs a computer, then it also needs a host to run in, then it also needs an attached keyboard/controller, also needs decent low latency audio output. All of this has to be setup, it has to work, it is prone to issues even when updating and like was already pointed out, prone to the developer just making it obsolete or like in the case of the latest Komplete Kontrol, ruining it with a redesign.

It is never outdated
Sure the sound of it may become "dated" or predictable but a synth from the 70s is still functional today and all you have to do is plug the thing in and switch it on.

Requires little knowledge to use
You do not need computer and technical skills to use hardware, often even without a clue of what it is a novice can figure things out purely by moving things and a synth is something that attracts people to want to play around, unlike a computer in the cornet of the room.

It is better to perform with
Hardware controllers with dedicated parameters allow far better overall control just by feel alone allowing quick switching between an ADSR slider and an LFO potentiometer or a mode switch button, you can tweak things often with far better results than with emulated midi controllers or point and click interfaces. While you can get some MIDI controllers to offer some hardware functionality, it is almost never the same as having those dedicated controls that have their own feeling and range. There are reasons live performers still choose to lug around heavy dedicated synths when we all know they could easily use a cheap controller and macbook. You look much more professional with gear than a box of software and a laptop.

You will tend to really invest your time and effort more in a hardware synth
I kind of feel that owning hardware at least for part of ones life helps more to really teach the fundamentals of how they work and helps you more creatively to be more "limited" to what is in front of you. There aren't software issues, crashes or other guff getting in the way, just whatever sound is being made and how that is affected by the movements of the controls

There are some caveats tho…

Hardware requires space
Synths are great fun but need space to fit in somewhere and this is a challenge for some. It is also a consideration if you like to be mobile or have a limit in what you can cart around for performing, a laptop and a MIDI keyboard can be far more convenient and less risky if damaged or stolen.

A Synth may provide you with just 1 collection of sounds
Depending on the synth it may offer great sounds but in a specific sound category so owning several synths requires more space

Hardware requires maintenance which can cost a lot
As hardware ages it may need some servicing such as cleaning, replacing potentiometers, caps, connectors etc and unless you have skills this can really cost to have someone specialised service your hardware.

Hardware in itself is often hugely expensive
Comes down to your needs and budget. If you are bedroom producer or someone just churning out tracks without any real dedication or love for a certain kind of method or sound, likely you won't see the benefit in a synth when you can purchase 50 plugins for the same cost you will likely barely ever use more than flipping through presets, but it gets you a much greater access to sounds.

Software Synths have presets
This is both a pro and a con in some aspects. While some synths have preset abilities often it is just what kind of waveforms and mods are applied, the position of actual parameters is not stored which leads many producers that want to save synth presets actually using ledgers to note down all the settings to be recalled especially when used in rerecording.

Presets can of course be completely saved for almost every software based synth making it super simple to recall, however this can also lead to lazy flipping instead of learning to design a sound. Why spend an hour making a great deep moog bassline when you can get something that will do in a few minutes of flipping presets. Greatly improves efficiency of finding sounds at the cost of learning the fundamentals of designing it from scratch.

There is the final point where some people just enjoy using physical gear. There is something about having a piece of hardware that generated the noise that you can really mess around and experiment with, connect it to hardware effects, try and attach something else to the setup, spend literally days on designing a sound since switching it off and on again everything is in the same place you left it. I would encourage people to check out this youtube channel if you have not come across it already which is an inspiring look into just why hardware is still a drawcard for many… It's fun and interesting, aspects sometimes lost when playing around inside the box.