I dont understand the saying "Ignorance Is Bliss"

Nor do I understand why people think its so true
It's not good to be ignorant

Not in todays society
Ignorance wont get you a job, a house, a nice car, food to eat
It wont get you anywhere

Why is it so cool to be so fucking stupid these days?

The amount of girls I've argued with over stupid little things and gotten myself worked up over when I know they have no idea what they're talking about
There is no point arguing with an ignorant person.

I still do though
I think I like proving to myself that I'm not stupid.