Asking this question in this way (demanding an explanation) frames it so that people will instinctively feel defensive. There’s no shame in being a virgin. You aren’t entitled to an explanation from anyone about why.

Because I never had sex.

It’s a pretty good movie, might watch it again.

Because some people apparently prefer to spend their time reading stupid questions online.

If you’re that old, you probably want to be, and that’s totally okay.