Why do they use autotune in hip hop music?

I thought you were suppose to use you're real voice when you are
rapping.

They make hip hop sound like pop music now- a- days. It's not true hip
hop. People use to listen to the lyrics now, they can't even hardly
hear what rappers are saying because they use so much autotune in
their voice. Plus, some of them be trying to sing and can't sing like;
Drake and The Dream.