By RAW anything can become dented and broken, but aside from shields and unattended objects I found no rules for just chopping at someone's weapon or armor, like in PF1's Sunder Maneuver. Not sure if they're very well hidden or just not there.
It seems to be a pretty arbitrary idea.
I get that the shield is absorbing damage. But shields didn't routinely break in PF for a long time and it didn't bother anyone.
If suddenly they take wear and tear, then why does armor not take wear and tear? And why doesn't the sword bashing into the shield take some wear and tear? I'm ok with one sword going through 10 shields before it wears out, but a sword ruining shield after shield without ever taking a nick is out of whack.
Which is NOT to say I want swords wearing out. I'm just pointing out that maybe shields simply shouldn't wear out.
Not only is it a bit of a pain to keep up with, but it creates a dissonance in the story when nothing else wears out.
I get that shields avoiding damage is a big new thing and to compare 1 to 1 against PF1 you can always gain the AC and never "block", thus your shield will never wear out. Status quo maintained. But, don't they want people to use this cool new feature? If encounters assume shields then they should be balanced in.
On the other hand,I suppose shields should be seen as functionally equivalent to temp HP. Putting a limit on the # of blocks in a fight puts a cap on the HP boost. And maybe they simply really need a cap. But they have created a serious weirdness in pursuit of that.
Well it's only wear and tear when you use the shield to reduce damage normal non-Damage reducing use won't dent it.