Horwath
Legend
For spells I agree, there should be Action and Bonus action spells.I mean, that one is simple enough. They want greater flexibility in how you can make use of those ride-along actions.
Consider something like healing word. In order to circumlocute around the bonus action cast time, you would have to do something like this: "You can cast this spell any time you take an Action or use your movement, so long as you are not silenced, but if you cast this spell during your turn, you cannot cast any spell that uses a spell slot with your Action, nor can you cast this spell if you have already cast any spell that requires a spell slot." You might be able to trim that down with careful editing, but there's only so far you'll be able to take it....
And now every spell that was a Bonus Action cast time has to be written with that extra text. In other words, you've just ballooned the length of the spells chapter by easily another 5-10 pages just from having to keep repeating this over and over...not to mention all of the spells that don't initially require a Bonus Action, but use one for continuing the spell's benefits (e.g. witch bolt; basic casting is Action, but getting the d12 lightning damage on subsequent turns is a Bonus Action).
All that, instead of just having the teensy bit of "complexity" of the Bonus Action, and saying that that's the category for ride-along stuff that you can only do a bit of, but you can do it while you do any other proper Action-y things that tickle your fancy.
Or if you want something pithy:
There are lots of things where it makes sense that doing X takes up all of your attention/time.
There are lots of things where it makes sense you can do them basically anytime.
But there are a fair number of things where neither of those make sense: it shouldn't eat up your whole attention, but it also shouldn't be free-use-whenever.
Turns out, having a clean, straightforward box to put category-3 things into is actually really, really useful as a design tool. Hence why every single WotC edition has had them, as did PF1e, and PF2e switched to a three-actions-per-round system to functionally achieve the same goal in a different way. Three-action things are what 3e would have called a "Full-Round Action", and the fact that you have three actions a turn means one of those can be spent on a ride-along action without it eating up the whole of your turn, and thus achieving the same end by a slightly different means.
If every character JUST has one singular Action they can use, you're always going to be bumping into things that would be really really nice as ride-along actions, but utterly terrible/worthless as "this is all you do during your turn".
Also potions/poison.
rage: free action
bardic inspiration: free action
Polearmastery: part of Attack action
Cleave from GWM: free action once on your turn
Divine smite: free action once on your turn
as for PF2, 6 action would be more custumizable, also 6 seconds round, 6 action points:
Action: 3 pts
Move: 2pts
Bonus action: 1pt

