Why doesn't pve have pvp combo structure?

[Seraphor]

And yet every expansion we end up losing skills and getting some back because people want new expansion skills, but we're simply at the limit of how many skills we should have.

Maybe if they could actually consolidate the amount of keybinds we have instead of outright deleting skills, we could finally have an expansion that actually builds on the job we played last expansion instead of one where half our skills magically disappear overnight.

Or they could just delete the entire Gnashing fang combo to make room for some new Endwalker gimmick for the Gunbreaker job, which is probably what's going to actually happen if they don't consolidate anything.

There's definitely room for button consolidation, but simply turning every combo into one button isn't the best way to do this. Many jobs have skills that are mutually exclusive, you can't use one while the other is available, or some skills simply become redundant in the presence of others.

BLM: Combine Ley Lines and Between the Lines. Have B2 upgrade into Freeze and F2 upgrade into Flare.
NIN: Combine Dream within a Dream and Assassinate.
SAM: Combine Meditation and Shoha. Upgrade Shinten into Seigan when under Merciful Eyes.
DRG: Combine Fang and Claw with Wheeling Thrust. Delete Piercing Talon.
PLD: Combine Requiescat with Confiteor. Combine the effects of Intervention and Cover, or simply buff one and remove the other.
GNB: Probably would make the Gnashing Fang combo here a 1 button combo, the same as Continuation. So that you simply alternate between the two just like MCH's burst phase.

There, that's all of the worst offenders in terms of button bloat out of the way. The only other jobs with 'too many' buttons are SMN which already does all of this sort of thing with it's Bahamut and Phoenix skills, and BRD, but that already only has 2 combo skills and I'm not familiar enough with it's endgame rotation to know what else to realistically be axed.

I definitely wouldn't combine the combos for the melee jobs into single buttons. Mainly because their combos is what their entire rotation is based around. You remove those and they're reduced to 3 button jobs.
SAM and MNK both have skills that simply wouldn't work with this sort of consolidation, because they unlock the ability to use combo skills out of order.
DRG has 2 very long combos, get rid of those and it has 2 spamming combo buttons and Jump.
Lastly, NIN, has a heavy burst rotation. It already spends half of its time simply hitting the 1-2-3 combo waiting for mudras and Trick Attack to come off cooldown, and it only has 4 of those combo skills to consolidate anyway. Combining them wouldn't achieve much and would make it more boring.