Hmm might as well just give us regenerating health since estus is infinite.
What a pointless comparison.
First of all, Estus you have a maximum of 12, before you have to refill at a Bonfire, respawning everything back.
Repair Powders you can have 99.
You can have 99 Life Gems and indeed it's a stupid mechanic they included, rendering the idea behind the Estus trivial already.
Secondly, being without health and finding a moment in the enemy's attack pattern to drink, it's a much riskier and strategic move than simply having to replenish your weapon durability, since you can do that at your leisure (your health can go to zero in 2 or 3 hits, the same isn't true for your weapon).
So it's not the same level of "challenge" at all, infact, the durability mechanic doesn't really pose any challenge, just extra shit you have to put in your hotbar.
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By your logic, let's have the same level of armor durability.
Everytime you get hit 1/20th of your clothes' durability goes down, so you constantly have to try new gear!
I think the "prepare to die" hardcore nonsense DkS has become famous for, is going to the developers' head in the worst ways, with some mechanics.
DkS isn't particularly difficult, never has been, but it has always been interesting in its challenge, not just an empty chore just to waste your time.
The durability mechanic, how is implemented in the Souls series, is exactly that, a waste of time.
More over, just to further point out the inadequacy of your comparison: It takes skill to never get hit, but it can be done.
Durability goes down no matter how well you play, it doesn't require any skill at all to handle.
Estus is there to fix your fuck ups, and you have 12 chances.
Repair Powder isn't there to fix your fuck ups, it's just there to keep you going if you're so good you never need to rest at a bonfire, basically the antithesis.
If durability was tied to well timed combos, then there'd be an argument to be made, which isn't the case right now.