Well, it's SE who added those achievements in the first place. If you are a completionist you'll want to do them regardless of the level.
Which has nothing to do with what the op accused the lv 50 of. Believe it or not, one can be level 50, get the achievement and still not be an ass towards the lower levels in the behest. I know it must shock all you advocates for solipsism, but it is possible for this situation to be a win-win one.