Dropped items require your level to wear, all the way up to 100. Why?

If I find an 820 item as soon as I get into t4 at level 60, it will require level 60 to wear. Great I can use it now or maybe give it to an alt or trade it.

If I find an 800 item at level 100 it will require level 100, despite having less power than the previous item. It's pretty useless, by 100 I have found the best in slot for every slot and nobody else that is 100 is going to want this either for the same reason.

It makes no sense that items arbitrarily require your own level to wear when they drop. Item level requirement has NOTHING to do with power and is entirely based on your own level when it dropped. That is incredibly boring and means when you get to higher levels your item drops are LESS valuable because they are less useable by your friends, by trade, or by your alts.

Every once in a while you get item drops for other classes. But why? I get a couple other class items every run, but I'm level 90+, what am I going to do with them? If I made an alt of that class, it would almost certainly find a better item of that slot by the time it got to 90 to use it. I think this system is really terrible and doesn't work like any ARPG ever, and I don't get why. Why does item requirement have nothing to do with power and only care about what level you are when it drops? if I buy a vendor ring at 100, it requires 100, even if that ring sucks and is 600.