I wonder if this isn't entirely age group specific. I'm in my mid-30's and in a very not-mid-30's life stage, but I too have been feeling a bit isolated lately. Since I'm stating professional school in August, I don't fit in with either my classmates (who are in their low-mid 20's) or my peers (who are having kids, and generally not interested in other things - or don't have time for them). Of my remaining friends, some are willing to bike/walk/hike, but most are much more interested in going to dinner at a fancy restaurant and then an expensive show (nothing wrong with that, but I'm trying to budget - and they sometimes aren't receptive to gently offered alternatives). I have also become a bit more cognizant of which friends are actually friends, and which find me (the lawyer) and DH (the tech guy) handy when something breaks and otherwise can't be bothered to respond. As I've been cleaning the junk out of my life, I have also been working on cleaning out the friendships that aren't really. Sad, but true.

I know that soon I'll be too busy to worry about it, so I'm focusing on getting my house (literal and figurative) in order. It's not bothering me - but it is something I had noticed.