At one point, we were 50/50 split; four husbands and their wives, all part of the same group. My wife was clearly there just to humor me and be social; she had little interest in continuing to game once the initial mini-campaigns we were playing ended.
Another wife was clearly there to socialize more than game, and in fact probably used the fact that her husband used to game in college as an excuse to get involved in this group again. Neither of them are currently in our group anymore, although we still see them and do other things with them from time to time.
Another wife was introduced by her husband, but clearly enjoyed gaming as well. She only enjoyed it to a point, though -- she quickly became bored if it wasn't a bit hack and slash in style. That couple has since moved back to Texas, so they're not part of our group anymore.
Another wife was also introduced by her husband, but also clearly enjoys gaming as well. In fact, at one point, her husband was ready to hang up his gaming spurs and give the hobby up, and she wouldn't let him, saying something to the effect of, "this is the only hobby of yours that I enjoy too, so we're going to keep doing it together!"

They are both still in our group, and in fact, she's running our Eberron game currently.
The rest of our group is made up to two men that have joined us more recently, and their wives also do not game.