So now you never break any laws? I don't believe you.
EDIT:
You have no idea, do you?
I'm speaking from my own experience. Some of these people are my friends, some are family. I know how this works first hand.
1) Many use one SSN for the whole family, others have an SSN, but don't have a job permission. Those who have the number, but not job permission, make fake SS cards. Many small businesses don't check SS of their employees, so they end up having taxes taken out of their paychecks. IRS doesn't care if they're illegal, they're still paying.
2) My examples don't commit serious crimes. Not all illegal aliens are blood thirsty latino kings.
3) Yes, my best friend's father died from cancer in this country. They paid for everything on their own, even lost their house because of that(yes, they were illegal and were able to get a mortgage)