Why not cookies for sensitive information

Question

I didn't understand clearly why cookies shouldn't be used to store sensitive information?

Answer 1

Because users/hackers/randomers can see them......

Answer 2

Cookies are stored on your local browser memory (session is stored on server side), so everyone can simple open it, read and use... So e.g. if your account information like password and username would be stored in cookie, everyone can simple stole this information and use it.