Why do people bother dodging aoe during trash pulls?

[Granyala]

90% because the reaction is automatic by now from content where orange glowy things actually hurt.
10% because, as a caster, most voids interrupt me even if they do trivial damage.

As a healer, unless you eat stacked ones, I won't care much.

Considering that more and more people pick up this whole speedrunning mindset it's no wonder people like me are a minority.

Are you new?
Unless we are talking leveling dungeons with first timers (or the few dungeons in which it isn't feasible due to wonky scaling or crappy leveling gear), wall to wall pulling is what people do and expect.

That has been the case since ARR. I still remember rather insane Brayflox hard or several Heavensward dungeon pulls, where I actually had to use healing CDs to keep the tank alive.
The 2 groups we get to pull now in expert dungeons is a bad joke by comparison. Any healer or tank that gets "stressed out" in these is simply playing the wrong classes.