I was in two brief relationships with the same person some 10 years ago. I am single certainly by choice, I'm a sovereign person who loves their absolute independence, I get to do or not do whatever I want, whenever I want. Committing to be with someone is not my thing.
Sometimes it's lonely when a certain kind of friend is not available. Befriending single people is always a gamble, if they enter a relationship they are likely to fade out of existence pretty quick.