Probably off-topic a bit here and I may get wordy, so I'll apologize in advance, but in regard to paying for weddings, I'll lump in college tuition and give a few anecdotal experiences.
First in regard to weddings, I believe a lot of the expectations vary from region to region. I'm from NY and in my experience, the brides parents pay for the wedding. However, I have also seen that NY'ers seem to think image is everything and try to one up everyone else. My wife is from the Midwest and expectations are not quite as high in regard to weddings nor payment by brides parents.
When I got married I was 30, wife was 25 and we paid for everything. We were not well off by any means and credit cards came into play for sure. And by everything, I mean everything. It was a Las Vegas wedding and we flew out my wife's family and paid for their hotels, we paid for all meals while they were there. My wife made her own wedding dress as well as all of the bridesmaids dresses. I picked up the tux rental for all of the groomsmen. Basically, if you were kind of enough to attend our wedding, you just had to get on a plane and show up and thankfully there were about 60 attendees. Most of my friends and family probably didn't think it would last. Laughs are on them! or me
Anyway, we got a gauge of how much a wedding cost and it took us about 5-6 years to pay it off in full.
My daughter is about to get married and she's 27. Her and her fiancée each make good money, probably 3-4x what we were making when we got married, even taking into account the 20+ years, they are in much better financial positions than we were. When our daughter told us she was in planning stages, we told her upfront we would give her $xxK for her wedding and anything above and beyond that was up to her. We also told her we would be there for her if she needed help with any decisions but this was her wedding, we were not going to get into all of the details and try to nickel and dime stuff out. If she wants to go all out, go for it, but it's on her. I'd estimate we are paying for 80% of her wedding and the balance is really not a burden for her and her fiancée so they can get the wedding that they want without going into any debt at all, while we are not going to be getting bills and asked for more money month after month after month. I think it's a pretty practical solution to the issue. When my sister got married her and my parents got into a pretty big to do about expenses as my sister wanted 400 people at the wedding and my parents were simply not going to float the bill for whatever she wanted, but that's a story for a different time.
In regard to college tuition, I think it's very necessary for the parents to have a sit down with the kid to temper their expectations. I am going to see this come to a head with my nephew here very soon as he graduated 4th in his class of like 800, near perfect SAT and ACT scores, well rounded kid, but a bit head in the clouds - he applied for like every ivy league school shy except Yale, and has been accepted to quite a few very high quality schools already (just off the top of my head, ND, UNC, Duke). Anywhoo, he is expecting to go to a school that before any academic grants are awarded is going to cost 30-50k per semester and I'm pretty damn sure that his parents don't have more than a semester full of college savings ready for him as they do pretty well, but they love to live above their means. I'm afraid my nephew is going to get crushed here because his parents just let him apply wherever he wanted and never made mention that hey, we really can't come close to affording any of these private schools, perhaps you may want to look for a few schools that you'll get grants or maybe a public school for a year or two.
I think there really needs to be some open communication between parents and their adult or near adult children about money, which is seemingly always a hard topic for discussion as is. I'm not saying I'm great at it either, as it's difficult at times, and my parents were certainly tight lipped about everything until I was in my forties - their only conversation about college with me was when I was a senior in high school and they showed me the bank account with my college savings totally $7,500 and said, here you go, take that into account when you apply for colleges! Thankfully I received a few scholarships, and only applied to one private school, got accepted but when no money was awarded and they told me it was $20,000/year, I was able to do some quick back of the napkin calculations and said, thanks but no thanks. Boston's loss if you ask me.