Why are Softballs hard?

Softballs Are hard because they have a type of metal inside it.

Because of the inside having to be a certain weight. The reason they are called "softballs" is because they actually are lighter and hit softer in your glove when you're catching, in comparison to regular baseballs, it also has to do with the fact that softballs are typically thrown in an underhand fashion rather than overhead or straightforward as many baseballs are.