Two things:

I think there are better ways to adress the button bloat that does exist on some jobs as it doesnt even affect a lot of jobs, stuff like undraw.

Remembering where you are in your combo takes a bit of attention that collapsing all combos into one button would automate away. Sure, no one is gonna miss a combo action when attacking a target dummy. But when something like firestorms together with your burst window is going on things might look a bit different. And keep in mind jobs balance is done for the harder content in the game. If you drift like a madman on a dungeon boss, why do you even care.

I do find it weird that some people act like collapsing combos is such a huge deal in terms of reducing button bloat but at the same time act like it's no big deal at all whenever they face pushback against the idea.