One idea comes to my mind pretty quick. If you're not using qwerty or have an unusual layout, keybinds for certain apps turns into a sudden project. It would definitely affect gamers who frequently switch games and rely heavily on default keybinds and standard keyboard layouts. Just switching to a basic qwerty layout for gaming would simplify that quite a lot

For me it's just aesthetic; I've used OEM (and OEM-like) profiles, XDA and SA. I've not found one to be definitely better than the others. There's definitely some differences to noise, but noise is something I don't care about.

Ergonomically I prefer flatter uniform profiles like DSA as opposed to heavily sculpted and tall profiles. Additionally, having all caps (or at least letters and numbers) allows me to rearrange things more to my liking. (For reference, I use a split ortholinear keyboard.)