Why Do Guys Prefer To Be Single?

I understand that a majority of guys who are in their 20s prefer to be single to focus on career, travel, or they’re not ready to settle down yet.

But I’m curious to know the reason why guys who are in their 30s or 40s prefer to stay single. Is it true that a guy has to meet “the one” or like someone that they really love to actually want to settle down with them?