Why is Eminem so handsome?

There are three possible answers here:

Firstly, that were he unattractive, he may not have become as famous, in which case you mightn't be here asking the question. It's a self-fulfilling prophesy.

Secondly, because he can afford the best makeup artists and cosmetologists in the World.

Thirdly, it's very likely that other Darwinian elements are at work in your forming the opinion that he is "so handsome". Likely, you're drawn to his success, independence, fame, wealth, his bad boy attitude, and general popularity, and all these attributes lead to your brain, naturally, finding that attractive. It's an evolutionary thing.