Why would he ask me the reason i'm single?

I (F, early 20s) was having a conversation the other day with a guy (M, early 30s) and the topic of romantic relationships came up when I mentioned something about my best friend's boyfriend. After I mentioned him he asked me if I have a boyfriend and I said no. So he went on and asked "Why? Is there no interest?" Couldn't tell if he meant interest from guys or from me. The way he worded it seemed a bit odd, almost like he was assuming men don't hit on me and I almost took offense lol. So what's the reason a man would ask a woman this sort of question?

Why would he ask me the reason i'm single?
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