So you all remember back when achievements were first added, and everybody was all excited about them, when they blatantly have no use? What if rewards were coupled with those achievements? Like for the open your inventory achievement, you recieve 1 chest. They'd have to be balanced of course, but I think it would be more motivation to complete them. And like the bonus chest, it would be completely optional in the event that someone finds it cheap.
Achievements can't give you a reward because they are shared between your worlds in that PC, and will be useless if you are doing them in creative, but maybe they could give you points or something to "buy" a skin or something like that.
That would be awesome