I didn't see anyone assuming that people who pay for weddings didn't pay for education. Some people do it all. It's a fact. However, I don't see anything wrong with not being willing to pay for everything. I don't consider that a parent's job. We have enough money that we "could" fund a wedding in addition to their educations, but don't see the need to give our adult children everything. If we decide to travel in our retirement instead I see absolutely nothing wrong with that. We raised our kids and set them up for success. At some point they're on their own. For us, it's after college graduation. If they have to sacrifice a little to have the wedding of their dreams I really don't have a problem with that.
I've watched some parents postpone retirement, postpone vacations, etc. to pay for weddings for their children while the children travel, buy cars, etc. I would happily postpone those things to pay for education, but not for a wedding. I also insist on equal sacrifice from my kids if we're financially involved. Different people, different choices.
I don't run in circles where people have the wherewithal to do it all without making sacrifices. If that's the case, they can pay for whatever they want to. The point is that putting some archaic rule in charge of who does what is silly.