Why do roses have thorns on them?

It is a defense mechanism they developed through evolution to protect themselves. Most animals don't like thorns and they are left alone. It is called an adaptation if you want to look it up. Another example in the animal world is honey bees have stingers. They don't need stingers to make honey or have babies, just to protect themselves.

The bible says it's because Adam disobeyed the commandment. Nobody has thought of any better reason. Deer love to eat roses. Evolution suggests that roses should have evolved seeds to be scarified in a deer's gut like other flowers did.

So you can snap the thorn off stick it to the end of your nose and say Look at me I'm the Wicked witch of the North.Gawd I love doing that!

You are in the right ball park ..for their protection.