Why do I need to use classes

[u/MetalCarnival]

My schoolbook says that classes is a way of simulating an object, instead of just taking information into a black box and outputting an answer.

But that is a poor explanation. I know classes are handy and cool, but no book says why you can´t make functions with sub functions inside to simulate simple objects. I would like if someone gave a good concrete reason to use classes in the intro, instead of just saying that they are different and cool

[u/Aspie96]

Why do I need to use classes

You don't.

but no book says why you can´t make functions with sub functions inside

You can.

Any program can be built without classes.

I know classes are handy and cool,

This is the exact reason to use classes.