Am I understanding this correctly? In the US, you can create driver's licenses and bank accounts with only a social security number?

In Missouri at least, to get a driver's license you need your SSN, your birth certificate, and some form of identification like a passport or a bill in your name at your current address.

as if it's so hard to give cynthia at AT&T a fake name and address.

it's much harder to get the birth certificate. The utility bill is only used to establish address, and making sure that everyone's address is up to date is not easy or worth too much effort.