Almost every company I've worked for in a quarter century has participated in the co-op program; we've had bright interns every year, and they all went on to work either for the same company or elsewhere.
Many people are satisfied with that, and have other hobbies outside of work other than going to meets with other programmers. Or those who have programming as a hobby would rather be actually doing that.
Also, people have significant others and families. Geek get-togethers are mostly for single people who don't have a significant other that isn't also a geek.