Is it because it could potentially cause anguish and emotional pain to your significant other?
Why? Someone tell me.
The real reason is "accidental" pregnancy, disease, and jealous lovers.
I can't imagine that you really didn't realize these things.
Why do you degenerates who can't be faithful bother to have significant others?
If yall are confused by other social norms: If you have to hide what you're doing you shouldn't be doing it.