It's patronizing because the asker did not always have children. Unless they started having kids at a very young age, they clearly have experienced the same kind of 'free time' anyone without kids has. With modern entertainment, it's not hidden knowledge what kinds of activities people do in their leisure time.

That, coupled with the question, offers the implication that they already know what the answers will be and simply want validation that the way they spend their time is superior. That's textbook patronizing.

OP may not have meant it that way, but it's pretty easy for it to come off that way, hence why the question sounds kind of patronizing.