ModularGrid

In my experience, the hands-on factor of physical hardware is just so much more fun.

I'm sure many people on ModularGrid are very proficient in computer-based music making, in fact any finished tracks generally end up being mixed and mastered in a DAW. Heck, the website even features a web-based modular music-making environment (TrueGrid).

So why use physical synths on top of that? There remains their loveable quirkiness and fun component (especially with analog). There's also various arguments saying that the resulting music is better in some way - but that's more of an endless, fruitless personal opinion / classic flamewar topic, which I will now blame you for re-introducing, and blame myself for elaborating upon.

The same reason people still like having old 8 bit computers instead of (or in addition to) emulators, cars that aren't electric, hand tools for woodworking, analog tape recording, vinyl records, letter presses, etc. The benefits are mostly about the tactile experience of handling the anachronistic technology, rather than the end result.

There is practically nothing one couldn't do with a software emulation of analog synthesis, but real hardware is more fun to play with for some people.

Different UI sparks creativity in different ways - you can see this in software as well. Having tactile hardware makes people approach music differently. Also some prefer the sound. Finally, many people program computers all day and are looking for a break from the screen. I'm sure there are more reasons but these are certainly popular ones.

You can do both. Each approach has its own pros and cons both in the sound and modulation options. Eurorack is all kinds of awesome for many reasons.

UI, immediacy, chaos/entropy, and compatibility/flexibility.

The UI of a modular is great. There is (generally, a few digital modules have menus/modes) only one function per knob/button/jack. Everything is pretty obvious as to its function. The workflow feels creative, in a way that programming CSound or MAX/MSP never did to me. I sit at a computer ~8+ hours a day coding as-is, do I really want to do that for my instrument? I generally just set ProTools to start recording, and then turn off my monitor and ignore the computer.

Immediacy of modular synths is amazing. The sound you have now is now, once you unpatch or turn knobs you aren't getting it back. Even if you take photos, you're unlikely to get it back again. That's part of the great part. It isn't a preset that you're using. You're using something that you put together. For live performance, this adds a really neat aspect of danger. Is there really much danger (aside from a system crash) of hitting 'play' in Ableton? No. But the modular can do all sorts of stupid things, which leads me to my next point.

The chaos and entropy in these systems is great. Sometimes you use patch cords that are too long and get some crosstalk/resistance that you weren't accounting for. Sometimes there's noise. Sometimes things skip and don't play in 4/4 as you were expecting (I had a weird clocking issue/ghost in the machine last week, that caused it to basically make its own drum fills... without any unit dedicated to that). For creativity, this is like a drug. The sound you're making will almost certainly not be the sound anyone else is using- period. That's pretty damn cool.

Flexibility/compatibility. Voltage is voltage. If you don't care about tracking pitches to a 12-tone scale, then there are practically no limits to what units will work together. A modular from the 70's can patch in with my current eurorack, and also my Minimoog Voyager- your software from 1970's probably doesn't work great with your iPad. My modular has stuff from around a dozen makers, and I have another dozen guitar pedals, mini synths, and such that also can deal with control voltage stuff. I can make little Arduino toys trivially that will work with it as well. I don't have to deal with different plugin formats, outdated systems (Protools TDM anyone?), inter-system issues, etc. It just works and that's pretty amazing.

Of course, I do have a computer hooked up to my recording gear, but it rarely gets used until I really have the idea ready to go. I'm thinking of getting an 8-track tape machine so I can remove the computer entirely.