I think it depends on the family. Younger kids just out of college will simply not have the money (our middle daughter will be more than $50,000.00 in debt when she gets her Master's in the spring of 2013) but people should stay flexible.
At our wedding, my parents paid for the reception and the invitations and
the open bar, I paid for the dress and the church, my husband paid for the tuxedos and his parents paid for.... nothing. Despite the fact that we had bought a house together, were already planning a wedding and were living in the said house together, his mother said I "trapped him" by getting pregnant and that people who have sex before the wedding don't deserve a wedding. They wanted us to elope and then lie to their families about the date the wedding took place, so the baby wouldn't look "illegitimate."
I said, "Balls." to that and did what we had already planned. Only we planned the entire thing in 6 weeks.
Even getting a guest list out of my husband's parents was like pulling teeth. Such wonderful rays of sunshine, those people...