I'm pretty happy with my life, I've never been someone that gets depressed when they are alone or gets upset about having quiet time to myself, if anything I enjoy that time a little too much. It's a personality type.
My lifestyle lets me be extremely selfish, not in a "rude to other people" way but privately. I pretty much only have to do things I want to do, there is almost nothing in my life that I "should do" even though I don't want to. I work 4 days a week and earn more than I spend, I'm not rich but I can blow a few thousand on a holiday (or something I want) a couple of times a year just because my expenses are low. I already paid off my student loans and my car, I only have a small mortgage left on my house. My life has almost no stress at all.
That can be pretty amazing, for example earlier in the year I felt like a holiday and with no notice or prior planning, 3 days later I was at a resort in SE Asia for two weeks. There is a lot of freedom and once you have been living like that for a while it's very difficult to reign yourself in and let yourself get tied up in obligations. I don't think I could live in a situation where your days are so full of obligations that you barely get to sit down and have a moment to yourself. I think having kids is like that.
I realise how the above sounds but I'm not a complete self-absorbed hermit. I have friends, I date and I enjoy spending time with people but my independance is important to me. In the rare times I have dated someone like me who also values their independance it was great but they were as reluctant about marriage as I am.
When I date we hang out like a new couple (joined at the hip) but after a few months I will need some space. I'm upfront about it but most people don't understand it. If I try and take space, they think that there is a problem with the relationship (even though i tell them nothing is wrong), so they keep trying to spend more time with me to "fix" it. It gets to the point where I can't handle it and just take the space regardless what they say. This will upset them, which creates drama at a time I am already dying to be left alone, it's a bad combination that usually ends in a breakup. I don't hate being single, so each time this happens I am not in a hurry to jump back into the mix and try again.
I'd like to meet someone and get married (maaaaybe have kids I guess maaaaaybe) but I find it very difficult to find someone who is happy to add to the parts where I want companionship without assimilating the parts I like alone.