1) Sounds produced by analog equipment cannot be reproduced exactly in software. You can get very close but so far nobody has gotten it 100% right.
2) The physical controls on hardware make the process of creating music more tactile / intuitive / emotional. It's faster to reach and turn a knob than to click on the knob and drag it -- maybe only by a little but when you do that thousands of times it adds up.
3) The constraints of using hardware can be a useful artistic limitation, that actually increases creative output.
I completely agree with (2) and (3), but have you really tested (1), with a blind testing technique and a considerably large sample size? I find when people are talking about how they can tell apart analog from (good) emulation, or 320kbps mp3 (compressed with a proper encoder from a high-quality source) from flac or wav they didn't actually try to do that in a statistically meaningful way.
Isn't it more than that though? It isn't just about sample rate and resolution which for a single sound should be extremely accurate, it's about replicating the effect on the sound as the knobs are twisted and sliders moved around. That's a whole different set of problems and I imagine very very difficult to accurately replicate/synthesize.
Here's an example: https://www.u-he.com/cms/diva -- it's widely regarded as one of the best sounding analogue emulations (mostly due to its filters) and as a CPU hog (in its "divine" sound engine mode).
Mind you, in a modern CPU you can still run a few instances, but very fewer compared to regular plugins.
2) The physical controls on hardware make the process of creating music more tactile / intuitive / emotional. It's faster to reach and turn a knob than to click on the knob and drag it -- maybe only by a little but when you do that thousands of times it adds up.
3) The constraints of using hardware can be a useful artistic limitation, that actually increases creative output.