Why do teachers ignore students that are crying?

A student was crying to me because he didn't get what he want it whatever. The teacher I work with said, "Don't give in. He needs to get over it and I'm done putting up with it." She ignored him. So did the other two assistants. Unless they have a problem at home, they ignore crying kids and go to the next kids. I think it's too harsh. The teacher said, "I know it sounds mean but we don't put up with crying in my classroom. If they have to cry, they can do it somewhere else! Yoy need to be a teacher and let them cry it out. Tough love. Kids need that. Stop giving in because it would be okay for them to get what they want from crying to you and you will get tired of it!" They got very upset when I kept giving it to the kids. I feel so bad when they're upset but the teachers tell them to get over it or ignore them crying unless they have a huge problem.