It's pretty handy for money laundering and buying/selling illegal goods.
If everybody used bitcoin for everything, then there would be no need for exchanges, payment gateways and the like. This stuff is added cruft.
People can't use bitcoin for everything, the network can't support enough transactions per second for even a small city of people to use it for everything.
Any statement that begins with, "if everyone..." is a fantasy.
If my granny had wheels, she'd be a bicycle.
You could add some ham and it would be a sort of British carbonara.