I'll answer from a supporter point of view. I made my survivor go to counseling after I realized that our marriage was not going to survive the Status Quo. That no matter how much we loved each other, we couldn't make the necessary progress on our own. Fortunately, he doesn't want to lose me and he's had therapy before, two points that really facilitated that he was open to agree with my point of view. I realize that my approach could have horribly backfired. We ended up both going to counseling, which I hope will yield results in the foreseeable future.
I think, often we think we can cope on our own until the point where it's absolutely proven to us that we can't. Like crazy_gecko's story about suddenly finding yourself on the bathroom floor cutting yourself and realizing what you're doing. If you're not at that absolute low point, it's hard to say: ok, I'm going to therapy now and make myself hurt by going through all this cr*p again. Because let's face it, it hurts. So your motivation has to be very good to willingly submit yourself to that.