Why doesn’t Paul Ryan Run for Prez?

I’ll admit I don’t know much about politics, I figured y’all could illuminate me on this. There was a time years ago when people were talking about Paul Ryan being a strong contender for the Oval Office. I would hear his name a good bit. But then, I haven’t heard that talk in a long time. He seems like he would be a good fit, he’s young and would be a fresh face. Probably has good ideas. Why doesn’t he go for it?