Why do adults and teens ignore crying children?

They get told to get over it and give it them hard. I work at a preschool and the teachers ignore crying children. I would give in but they get upset because the kids are manipulating me and I can't even see it. When a child is crying I can't help feel bad, even when they deserve the punishment. I think teachers are becoming meaner and meaner. I got told I'm too nice and I need to give them tough love.