At 50+ I remain an independent agent. Lots of thoughts on this, but I always start with: why be married, unless you have the perfect partner?
So you're "not alone" when you die? That only works out for one person in every couple, even if it lasts to that point. A lot of folks find that they end up dropped when the going gets rough.
So you have someone to take care of you when you're old and feeble? There are ways to put off feebledom until the last few months, with work and reasonable luck.
So you have someone to carry on your name after you die? Who cares, I'll be on to my next lifetime. Other than that, who needs to be worried about the near future for youth? Kids are home forever for those with young ones today.
So you look like a "normal" person, for social purposes? I prefer to ignore the normals... why would I want to be one?
I could go on. If I had the perfect partner, I'd go for that. It is always a gamble whether that will work out... and I haven't met any one who made me want to take that gamble. I can't imagine how I would survive coming home to someone who has come to depend on me when I no longer get a charge out of the situation. Most of the marriages I have watched over time have either exploded with considerable collateral damage, or survive on life support at the expense of a real life.
I'm probably a little unusual, I can go for weeks without speaking to people, though I have good friends whom I love. I just enjoy my life a lot as it is, and I value my moment-to-moment freedom immensely. I enjoy my obsessive hobbies, I ride a bike every day, I play music, I listen to music, I read a lot, I have cats who keep the home homey, I know how to connect to people when I need to. I can explore my philosophy without undue interference.
Above all I can attempt to live an authentic life, fully addressing the call of my interests and drives. My married friends have schedules determined by others, from the time they get up in the morning through to death. I have to go to work, but I enjoy that, and then after, I crash through the door, run across a field shedding my clothing, laughing madly as I disappear into the sunset. Then I eat exactly what I want.
A life with a perfect partner MIGHT be better than that, but it is pretty good as it is.