It doesn't make sense to me to rush into marriage for a lot of reasons, but from my own observations (for context, I am a woman in my 30s and never married), here is why I think people do it and why all the hoopla. To be clear, I am not aiming any criticism at solid, happy, healthy couples. Here goes:
--Being married, especially for a woman, carries a certain social status. A lot of women give into that bullshit. And, to be fair, it is hard not to feel like there is something wrong with you/like you are undesirable if you don't have a ring on your left hand due to social pressure. This kind of programming can be overridden, but you have to do the internal work, or be wired a certain way.
--Going off of this point, some people are so desperate to be married and to not end up alone. Even otherwise intelligent people can and often do make terrible choices of marriage partners based partly on this. Fear of missing out. That, and a lack of brutal honesty and subjectivity about the realities of the situation. Seeing a partner as who they want him to be as opposed to who he actually is and how he actually acts.
--Emotion-based decision-making, as well as a short-term perspective. Not thinking long-term, and not being practical or realistic.
--The attention, glitz, and glamour of the wedding day. It is like prom amped up to 11.
My own take is that I would rather keep on being single than with the wrong person, or with someone who brought me down. Do I get lonely sometimes? Yeah. Companionship would be nice. But, my first loyalty is to myself. I owe it to all that I have endured, powered through, and overcame to live the best life as I can, and to live it well. Being with a good man might be incredibly liberating, and add a deep beauty and richness to my life. Being with a bad one would destroy everything I have worked hard for. So, I am selective.
And, too, I take marriage and commitment very seriously. If I am going to give my all to someone, he has to be worth it. Is he someone I would and could take care of if something catastrophic happened, God forbid? Would I be able to sacrifice in that circumstance with love and gentleness? Can I trust him with my body, heart, and mind without hesitation? Can I expect him to be faithful, and to stay around? Is he the one I could still love even when he drives me crazy? Am I willing to stand by him in bad times and make those sacrifices? These are the things I think about.