I was lucky, and about 10 years ago joined, as an under-30 legacy, the full-service -- golf, tennis, pool, dining, workout facility -- country club that my wife grew up going to. While I have a wife who's very understanding about my golf addiction, like Chip I would not have been able to justify joining a golf only club at that time -- and have a snowball's chance of adding one as a second club now!
Golf is clearly the most important single piece of the club, but the other parts [except the workout facility] are all pretty important to us (a family of five). I try to play early on the weekends, but often rather than heading home, I'll meet my family at the pool, where we'll have lunch and spend the afternoon. My kids play a decent amount of tennis, we use the family dining room quite often, and I spend a lot of money in the "pub." I can't remember the last time I ate in the adult dining room.
So the bottom line is that while golf is clearly the most important part of the club to me (and, I guess, my family), there's no way I/we would've joined if it was golf only -- at least for a cost somewhere around current club costs.