As a 20-something member of the New York meetups, I wouldn't want to hang out with the group if I were an older person. Unless I were exactly the right kind of older person (don't know much about CronoDAS' dad), I would feel alienated by a variety of in-jokes and other subtle cultural phenomena.

Similar to how, at my family's thanksgiving parties, I prefer to hang out with the "kids" (now young adults) in the TV room than with the older people in the dining room. (I share a lot of common interests with the older generation, we talk about politics and religion and philosophy and stuff that I'm interested in, and I enjoy it for a bit, but eventually I just want to get back to my peers).