alt Hacker NewsPretty much my experience. My pre-teen childhood was the 1970s. My parents had dinner parties or cocktail parties at home at least a few times a year, and so did most of their friends. We often had a sitter for the night while they went to these gatherings. Some time towards the end of the decade, and certainly in the 1980s, this pretty much stopped. I asked about it once and my mother said that hosting these gatherings was a lot of work and fewer and fewer of their guests ever reciprocated, so they just stopped hosting as well. I do think that they did it mostly out of obligation or "just the proper thing to do" and not because they particulary enjoyed it.
I wonder if it's all just downstream from class. It used to be that rich people would regularly host feasts for their dependents as a form of patronage. This was then imitated by the gentry and bourgeois: proving that you have a house with a bunch of servants who can serve multi course meals, showing off your etiquette and conspicuous consumption so everybody can see how wealthy and classy you are, just like the real rich people who are generous to their friends and get to flex how cool and rich they are.
Then at some point middle class Americans began copying these sorts of upper-middle class styled parties (again, as a form of class signalling; maybe partially because all the rich people in the movies and on TV and in magazines are doing it, and you want to seem like them), but Americans also fancied themselves as classless egalitarians, so it didn't really keep because the whole "conspicuous consumption" clashes with modern suburban ideals.