This is mostly true for the sound of the instruments – the emulations are very good these days – the folks writing them often sit with the original instrument and an oscilloscope and adjust the software until the outputs are the same.

But there are two things primarily that you get with physical instruments:

- A bunch of limitations. You're more likely to dive into deeply understanding your instrument if it can only do a well-defined set of things. This is counterintuitive, but absolutely true. If you're using VSTs, you should similarly force yourself to use only a small set of them, and to swap them out very rarely.

- A tactile interface. Generic MIDI controllers just don't do as well. There is a gap in playability between the two.

That said, I usually explore on a physical synth and often end up using a soft-synth in finished tracks. A physical synth is a lot more fun to jam on than a MIDI controller. It may be possible to build a physical controllers or modular controllers that captures more of that feeling (and a lot of high-end physical synths these days are just ARM systems running real-time Linux), but the run-of-the-mill MIDI controllers are not that.

(Reference: have worked for two companies that produce VSTs, including the biggest of them)