Does weapon durability and breakage force the player into some similarly engaging new-weapon-acquisition mode of playing or does it amount to mindless inclusion to pad game-played time?
I'd just add it to prevent people from smashing their way through dungeon doors without consequences. Not necessarily to pad playtime.
But that would eventually become one effect of course, either by making you look for new weapons or by making you visit the next anvil to repair whatever you broke.
I think it's an okayish concept to "punish" the players for treating their equipment badly. It's not the most exciting one though.
In Arx it was kinda funny, because you'd take the hammer and click your weapons "healthy".
Bit of immersion fodder and more on the level of baking bread in Ultima. Which can be fine.
But to take a step back: The whole question is more about punishing players for breaking doors. Adding weapon durability is just one way to do that.
So to rephrase that question:
How should players be punished for breaking doors?