I am 45. I have lost track of whether this makes me young and carefree or old and wise on this thread. I am an intermittent poster, not part of any clique.
MN is far from representative of the world at large. Apart from anything else, it is predominantly women, so the views are going to be skewed by that, let alone getting into the detailed demographics.
I would never stay in a hotel if I could stay with friends, even ones I don't know that well. I hate hotels, you lie there listening to people you have never even met flushing loos, watching TV, banging doors etc. Maybe I have stayed in too many for work to see any fun in the anonymity these days.
I have never had a friend choose to go and stay in a hotel rather than with us. I would actually be really hurt if a friend did this. We have space and an en suite off our spare bedroom, so there is privacy for those who want it.
I have never turned up on the spur of the moment, but I am pretty sure my friends would not mind if I did, because they are friends. I also don't mind if friends do this to me, they are people I like or they wouldn't be friends. I aim to make my home as open and welcoming as I possibly can.