Because Apple thinks nothing of spewing these turds all over every machine and directory you visit from a Mac, which is not just a dick move but also technically incompetent.
The next Mac visitor who comes along will overwrite the turd with his own, so that's a blunder.
Then there's the fact that they could have stored all the turds on the local machine, keyed by URI or path or network address. This would solve both the dickishness and the overwriting problem. And if a remote machine's path or address changed, whoop dee doo... you lost your Finder layout for that directory. Pretty low stakes.
