I've mostly kept a couple work friends per job but I'm also more proactive than most people on staying in touch. When I was a kid I was awful at it and was a loner and eventually decided I would try harder to stay in touch with people and not let friends disappear because of a move.

But regardless of whether you keep them even with an active non work social life I want also want a work social life. I have your solution but that still doesn't remove my desire to have work friends too. I spend 40ish hours a week on work. I don't want that to be with people that I can't call several of them good friends.