Some of us are happily married and actually like our kids... its not 'romanticized' its just the truth, theres no one I would rather be around. I literally get to live with my best friends and yes being a mam have times when they stress you but I wouldn't change it for anything as they are still my favorite people. It must be sad to be married to someone you hate and I feel sorry for the kids whose parents hate them for existing.
In that vein people that 'romanticize' being alone (not things like going out on a day out alone for me time but those pretending every other human is the issue and they want to live on a rock miles away from everyone). The people who insist partners, family, friends are too much hard work and your better without any of it. Even shy/introverted people don't revel in loneliness they just have a small circle of loving trust cutting out the bigger lake of more casual friendships.
Isolation has been used as a cruel punishment for millennia and has scientifically been proven to cause MH issues and to be a huge crisis issue in the modern world. I assume people that do proclaim it are attempting to 'self protect' from the fact they have ended up lonely and it makes them feel more in control to pretend they 'chose' to have it that way. As they say though 'Just because you tell the same lie thousands of times, it doesn't suddenly become the truth'.