In the case of 1, it's just a legal thing. Used resale is a valid form of purchase, so the point is that you've purchased and not simply stolen (via download) a copy.

In the case of number 2, it's a matter of pride. Lucasfilm has the resalers money, not yours. The guy that has your money is the resaler, who does not pass it on to Lucasfilm (he did that prior). I realize that doesn't make as much sense in terms of marketplace economics, but it's really just a matter of personal pride, at least for me.