Why is the woman angry with her son?

M: You look furious, Mary. How come?
W: My son had an accident. He wasn’t hurt, but my car was damaged.
M: But it wasn’t too bad.
W: Sure. But he is still taking driving lessons. He just ignored my warning.
M: He should have known better.

M: Do you believe it, Mary? Accessible use of mobile-phones over many years could increase the risk of cancer.
W: Well, I read that article too. But I doubt it. There are huge question marks over the reliability of the data.