Preferences of this sort might be interesting not because they describe what their holders will do themselves, but because they describe what their holders will try to get other people to do. I might think that diverting funds from luxury purchases to starving Africans is always morally good but not care enough (or not have enough moral backbone, or whatever) to divert much of my own money that way -- but I might e.g. consistently vote for politicians who do, or choose friends who do, or argue for doing it, or something.