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.