I long ago realized that we are not the average couple, either in the US or probably in this forum either, but for Silicon Valley, we are totally average. I think I can count on one hand (with fingers left over) the number of friends who had parents pay for their weddings. Part of it is personal responsibility: I think there is this idea that if you are old enough to get married then you are old enough to pay your own way. Part of it also must be that few people here marry before 28+ so by then you had better be established financially.
For whatever reason, the pattern I have seen in my friends goes like this: meet great person in college and start dating, continue dating as you start career/do grad school, move in together at some point along the way, buy house together, get married.
With my parents, they told us in advance they would give us $x as a wedding gift and we were free to do whatever we wanted with it, whether that be spend on wedding, go into savings, or towards a down payment. We went with the maximum stress route and decided to switch jobs, buy a house, get married, and graduate from grad school (me) all at the same time. Thankfully we had plenty of savings between the two of us that all of that was possible! I definitely don't recommend taking on that much at once though. There are better ways to spend a honeymoon than figuring out how to send in bank statements to your mortgage officer from half-way around the world. :)