cause right now they're pretty useless. The idea of "learning your enemies warding habits" is a cool though, but, is completely useless for 2 reasons:
Lee Sin can now ward hop to both allied and enemy ward debris.
If you're playing against people that only ward in the usual spots, or you've got a great understanding of the vision game as a whole then yeah, ward debris isn't going to be as meaningful for you. If you're a newer player trying to figure out how to use pinks/red trinkets well though, or you're trying to get a read on something pretty specific (e.g. whether the enemy team's been warding across baron/dragon wall at all) then that's the sort of case ward debris is intended to serve. It's a deliberately small, simple feature, not something that's designed to occupy a lot of mind share.
It's good for non-support mains to learn how to ward.
At least they're subtle enough for any "experienced" warders to not really notice them.
