I think whether or not it is so important that you would break up an otherwise fine marriage is a choice.
In my marriage sex is not required, as a matter of fact our relationship has VASTLY improved since we stopped having sex about a year ago.
My dh always had a weaker sex drive than myself, so our entire sex life was basically only happening when I initiated and more often than not he would reject me.Even when he didn't reject me the sex was mediocre at best: mechanical, no passion...
I was sure that my marriage was doomed, it had been rocky since the birth of our DD and the constant rejection made me feel awful.
I thought for the longest time (we have been together for 15 years) that sex was required, that "I" needed it to feel connected. Well, turns out I don't.
Since I thought it was the end of our marriage anyways I decided that I would no longer "beg" for sex. I figured it would just peter out and we'd eventually separate - but quite the opposite happened: we actually started liking each other again.
I guess not being constantly rejected made me a lot happier which in turn made it easier for me to react positively to DH. Because of his low drive he doesn't miss it and surprisingly neither do I (at least not as much as I thought I would)
Is it the ideal solution... NO! But we have a lot of other things going for us: our daughter, our home, financial security, we like spending time together and have shared interests. We don't fight very much any more either and enjoy being a around each other.
Yeah, I would like the perfect Hollywood husband that has the hots for me and can't keep his fingers off me - but I will not leave a perfectly good marriage to a perfectly good man and wonderful father to chase some selfish physical desire. I made a commitment for better or for worse and I guess I good a good mixed bag.