I think of myself as making new "fabric". It's amazing how much new "fabric" you can get from crumbs!
I like to make them when I want "mindless" sewing...something I don't have to think about or concentrate to do.
I have to be in that mindset, though, or else I'm thinking about everything else I "should" be doing instead of making crumb blocks.
I've made blocks but have yet to join them together into anything. It is more like one of those "on-going" projects...kinda like string blocks. I make them when my scrap bins start getting too full.