That leaves us with …
Either the guy or girl says no
The dating goes bust.
First of all we must remember that during the late teens and early twenties identity and emotional difficulties come to fruition. If they’ve been festering inside this is when they burst out (quite silently may I add) and the person who is experiencing this most likely is to embarrassed to share.
Someone with emotional issues shouldn’t be dating at all and must get help. However, they’re too afraid to share so they date and fail.
On the other hand, when one side or both don’t know who they are, they don’t know with whom to date so they say no to a plausible person or they select the wrong person and the dating fails.
Some people are selecting who they think they want to be, or their parents want them to be (etc), and the dating fails. (Or the marriage does, or they live miserably)
Obviously the minority have emotional or psychological issues.
That leaves us with identity.