why do you think dads are so insecure when it comes to their daughters dating but not their sons?

Good question.

I think most good dads have an instinct to protect the women in their families, but naturally expect the boys to be emotionally tough and find their way - even when their hearts get broken.

My mother used to say, men know what men were like and what was on their minds when they were that age.
They are usually clueless about the girls their sons are dating until mom steps in. Ha ha.

Because my son is not going to show up on day saying..daddy I'm pregnant.

Dad's know what boys do

Because I know what her mother did when she was a teenager.

It's the idea that guys always have the power in any situation involving girls. This is why so many people think guys can't get abused by girls. It's the result of growing up in a patriarchy.

Pride/honour

Because they were once a teenaged boy and know what boys want

Cos most of them would date their daughters if it was socially acceptable and are jealous that other people get to date them instead

because he knows how men think

Because they know what men are like

Don't want their daughters being DNA dumpsters.