Excellent point! I think it’s a generational thing — Boomer and Gen X parents certainly had barriers to making and keeping friends, but not as many. I think it’s the unique, recent American culture of parenting that makes it harder than it needs to be.
The key is, I think, not making your whole world revolve around your kids. It’s going to happen to some degree — if you’re a decent parent anyway — but keeping the knowledge that you are a separate person from your kids is important.
I remember being taken with my mom to visit her friends, and being expected to entertain myself while they visited. If the friend had kids too, it was a lot easier, of course. But the expectation was that kids needed to learn how to behave, and that adults had every right to engage in conversations or games with other adults, without the kids constantly demanding attention. Whining or otherwise trying to suck all the air out of the room was not tolerated: We were expected to go outside and play (when the weather was nice) or go into the kid’s room to play or watch a movie or whatever, and LEAVE THE ADULTS ALONE. That right there seems to have become taboo nowadays — we’ve come to believe kids have to be hovered over, entertained, and catered to every second of every day. Children need unstructured time, and adults need adult time (alone or with friends). Stepping back a little, setting boundaries and enforcing them, will be good for both parents and kids.
*Note, obviously, this is only appropriate for kids above a certain age.