I have been thinking the same as you, OP. I am reaching 54 and about to start a 'new career' but in a similar field to the one, I am already in. I own my own house and have made some pension provisions, but I cannot retire anytime soon.
However, even if I had the financial means, I wouldn't want to. While I could find things to do, I have lots of hobbies and interests; I think I would get bored eventually. Also, I really dislike the wintertime and going out to work gets me through those months. Especially since many of my hobbies involve the outdoors, and doing stuff outside in the cold and rain are not much fun.
I often wonder what people my age who have retired do all day, every day. I am not one for sitting around watching TV or reading books. I love travelling, but I have already travelled extensively worldwide (although there are plenty more places I want to visit).
I think the 50s is too early to retire. Bearing in mind you could live to be 90, that's 40 years of finding stuff to do, and I can imagine you would get through a lot of money in that time.
If someone has had a stressful job and worked long hours most of their working life, they may feel ready to retire in their 50s - that's not me, though. Plus, I still enjoy the social interaction of work and the new field I will be going into.
Each to their own, though.