That group of my high-school friends who are now largely janitors, retail clerks, and dropouts? They get together pretty much every weekend, usually with spur-of-the-moment plans made on Thursday night or Friday morning. My wife often just invites a friend over for Saturday brunch; occasionally I'll wake up and they're chatting downstairs. I remember one time when I was still at Google, I'd gone over to a friend's to play Starcraft, but his roommate was trying out different cellos and he had played the cello in high school, so we ended up with an impromptu cello trio in the living room. Another friend dropped by unannounced, we got the fireplace going, and when the third roommate arrived home, he was like "This is like a scene out of the 19th century."
The thing is, this is largely incompatible with spending long hours at work or doing things in your off hours (applying for jobs, going back to school, learning new programming languages) for career advancement. I haven't had a moment like that (other than ones my wife initiates) since leaving Google for a startup - I suspect my friends (or some subset of them) still do, but I'm often too busy to be worth inviting.
I think that the number of comments here suggesting a technological solution - an app, societal change, whatever - is pretty amusing. Technology is not going to matter. What does matter is making a decision that friendships and relationships are important to you, and seeking out other people who have also made that decision. And accepting the trade-offs that go with that. There are plenty of people who do live like that, but they are largely not the folks on Hacker News.