I Don't Get It, I Don't Just Don't Understand

Ok, have to rant and get it out....

At least once per day I get a message from someone that is honestly shocked, or trolling decently, that I have a couple adult groups or posts because I'm Christian...

Why does this surprise people?

I have 12 siblings.

Christians have sex.

A lot.

Does the world just assume we split off random body parts and they turn in to children?