Personally I don’t, but I can see it would be an issue for some people.
How many Taiwanese do you meet who tell you that their fathers are in China, more or less permanently? There’s a hell of a lot of them, and even if they are being faithful to their wives the fact of being married isn’t sheltering them from the economic realities of the world we live in. Kid’s don’t always get the benefit of a two-parent family just because their parents are married. (Or are we going to define marriage more strictly to make it impossible for one partner to do what they feel necessary to provide financially for the family?)
Also, you don’t have to be married to be in a long-term, stable, monogamous relationship. I’ve known various people who have seemed to be able to raise kids together without signing any agreement to spend the rest of their lives together.
Consider this:
You become sexually active in your teen years and have your fun until, say, your mid-twenties. Then you meet someone special and settle down together in a relationship that looks set to continue forever. You have kids, and provide a happy, supportive, stable home, or whatever it is you’re supposed to do.
At some point you and your SO discover that you’ve run out of things to say to each other, or you’ve grown apart. There’s no animosity, no recriminations, maybe neither of you have even met anyone else. You just aren’t committed to each other any more.
So you stay together, because you have kids and you have a responsibility to them. At some point those kids are ready to start living independently, and there’s no need for you two to stay together any longer. You’re both under 50, with a whole lot of living still to do in the second half of your lives.
Your kids understand that you’re going to go your own ways, still be friends with each other and still be their parents. They’re mature enough now that your needs are greater than theirs and they agree it’s the best thing.
But you’ve signed a bloody contract which says “til death us do part”, and promises are made to be kept.
Marriage was (possibly) a necessary institution in the days when lifespans were shorter. I believe that in the modern world it would be insane to make a lifelong commitment to anything, because that’s a mighty long time and the rate of change in society and the individual is much higher. You can get married today, give it a quarter century and come out of it a totally different person with another 50 years of life ahead of you.
I don’t envision getting married because it’s a commitment for the rest of your life, and mine has barely started yet.