That's a fair point, but there are also many of us who
want to be friends with our co-workers, and not just see them as little automatons that we interact with for 8 hours a day, 5 days a week, and never again.
Personally the kind of companies I prefer to work for are exactly the kind where lots of people are genuinely friends, where they do group activities (voluntary, of course) together outside of work, and where people actually like and enjoy each other.
Likewise with the company I've founded... when the day comes that we have employees and all that jazz, I do care about "cultural fit" and I would prefer to bring in people who want to be in that kind of environment. It has nothing to do with wanting to control anyone's "outside of work" life, or denying them "separation of work and personal", it's just that it's more fun to work in that kind of environment and also, IMO, more productive.
None of this implies that we would ever demand that someone sacrifice elements of their personal life in favour of doing things with co-workers, of course. And we would not be doing group events where participation is mandatory or where you would be "dinged" for choosing not to go. It's just that I like working in a very collegial, friendly, inviting culture where people genuinely enjoy each other.