I'm single. Didn't choose to be that way, it just sort of happened. I was happily married but things didn't work out. I would much prefer to be married (or in a long term relationship) just because I am not solitary by nature and I like having someone to talk to. I know, it isn't all puppies and roses, been there, done that, but all things considered I preferred the married.
I have talked to quite a few married people over the years and almost without exception, if the subject comes up, they talk about the freedom of not being married. They reminisce about how great it was to be able to go where they wanted and do what they wanted, when they wanted.
I wonder if that is a part of the human condition, to be unsatisfied with what you have and yearn for the different. We single people want relationships, people in relationships want the single life. I wonder if there is a middle ground.