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.
Too busy watching the 40 Year Old Virgin
There could be lots of reason for not having sex:
Asexual
Low sex drive
Never found a person they could connect with like that
Being an awful person / falling into the internet incel category
Different motivations in life that they didn’t feel the need for sex
Medical problems - this could cover a lot from psychological issues to physical issues
Fear of pregnancy / failure of birth control
Strict religion
Nervous/anxious/shy/awkward personality (like in the film)
Because some people apparently prefer to spend their time reading stupid questions online.
It’s a pretty good movie, might watch it again.
It’s been such a long time that I can’t actually remember what happens outside of the waxing scene. Time to watch it again.
If you’re that old, you probably want to be, and that’s totally okay.
