Hardware is much more hands on, with real dials, switches, and other means of physical interaction which screens and mice don't come close to matching. Hardware does exist through which musicians can interact with computers, but it's usually MIDI, which has its own limitations compared to fully analog gear.
With hardware you generally don't have to worry about software or OS updates, and the hardware generally continues to "just work" for a long time.
A lot of uncommon analog hardware is very unlikely to ever be modeled in software, so the way it reacts when manipulated may never actually be matched in software (even when the potential to do so is in principle there if anyone ever bothered to create a high quality model of it in software). This extends to how it sounds as well, for the same reason.
That said, modular synth software like this is still great, and may be the next best thing to using the real thing. It's also a great way to learn and get a taste for what's possible before committing money to buying any hardware.