Putting gates everywhere not only costs precious stone but It weakens your walls, this leads to very few places to climb your own walls.
And it eases the pain point of mangonels, Because I would not mind if my units could more easily spread out via multiple entrances instead of all trying to climb up a gate that’s already in the sights of the enemy
I have used enemy walls for my ranged units more often than my own walls and the same goes for my opponents as well.
I feel walls are underutilized to put units on top of them and having it easier by lower the bar of entry to use them would help. Something that doesn’t cost resources and allows only the owner and their allies to climb one side of the wall via an entrance.