OK, so you yourself don't know why. Fair enough. Do some soul searching then. But virginity is something larger than the physical virginity you're focusing on. We humans have complicated emotions around sex for some evolutionary reason. It's not the case in general in the animal kingdom. Of course, we are serial monogamous generally speaking, but we aren't strictly monogamous. This is a fact. Even when you are with the one whom you love, you will still lust others, even if you don't cheat. Personally, I think virginity is something not that important. What's important is loyalty. I was like you when I was religious, but now I find having sex is something natural, not spiritual or sacred as religions trying to portray it.