I love my single life - I've been on my own for nearly 7 years. I'm 34 and can't see me ever entering a relationship again - I'm at my happiest without one. And don't want children :)
I'd echo a lot of the positives on the thread already (we did have a happy singles thread going for a while but I haven't checked in for ages) - for me the only real downside is that it's more expensive to live alone than to split bills etc with a partner.
I don't lack for company, most of my friends are married and lots have children but they're all more than happy to come round / go for dinner / chat for hours on the phone / go away for weekends with me / etc and that hasn't changed with their getting married. Covid has had an impact but only in that I can't hug my friends and I find that very hard. I still see them!
Sex wise I'm celibate and happy with that, I have a good sex drive when I'm with someone but not fussed at all unless there's someone I'm attracted to, and I don't form attractions easily or lightly, it's usually after I've known someone a long time. I often wonder how people have time for sex when I barely have time to sleep 😂
I've never really felt lonely since becoming single and while I understand pp comments about not being the centre of someone's world, I don't find that's true for me - there are now a whole bunch of people who if I didn't show on our daily chat or whatever would know something was up and would come to my aid. My friends dropped everything to help when my Dad was in hospital and passed away, and I didn't feel the lack of a partner then either.
Society doesn't like it much but I give no fucks about that - I've got my life exactly how I like it and I love my days, my weekends, my time on the planet. Can't see me ever giving it up for a man 
I get to have my home exactly how I want it, do whatever hobbies I fancy, see who I want when I want, run my businesses on totally weird night owl schedules, have toast for dinner and fill my home with books.
There aren't any downsides for me, but we are so conditioned to think that coupling up is what we're meant to do and staying long term single is a failure that it can be hard to get past that mental block!