I think that this is just another one of those cultural differences between Southern rush and rush in the rest of the country. Up here in Wisconsin, it would be simply TACKY to ask anything about your parents and their professions, be it during rush or for a recommendation. One sorority up here DID ask what your parents did for a living and all of us rushees were just
after the party. It's just not done.
I think that outside of the South, you're a lot more likely to find girls who are paying for their own sorority dues (I do!) instead of having their parents pay for it. In the South, where going Greek is more expected, it makes sense that more parents pay their kids' dues. I know that at least a third of my chapter pays for their own dues, so we'd never think of asking a girl what her parents do for a living in order to confirm that she can indeed pay her dues. At least half of the staff at the local Express are UW sorority girls.
This is another one of those reasons why you shouldn't send a travelling chapter consultant from a Southern chapter up North (or vice versa) without letting her know what she's getting into . . . There's just so many differences to keep track of!