It's pretty clear that the combination of having little social life and being single gives you more time to explore programming in your spare time.

Either one of those things can be very detrimental to programming outside of work. Not saying this is all romantic relationships, but it's very common for a partner to have an expectation that you spend a significant portion of your outside-work time with them. And single people who have a social life also can let socializing monopolize their outside-work time (though of course there are also people who may only talk to friends once or twice a week).

For many (including myself) it's really hard to balance relationships with solitary hobbies.