I date younger guys (and guys around my age too) for a number of reasons. But the most relevant one is that many guys in their forties are BORING. Many are very set in their ways and have limited things to talk about. Like job, health, pets, finances, mortgages etc.
When I am with younger guys, I usually feel connected to culture and what's happening in the world. I usually discover new music, fashion trends, ways of talking etc. And I LOVE that. And because I have a very wide and deep knowledge of music and art, I am able to bring that back to the conversation and most interesting younger guys love finding out about connections of current trends and music with past trends etc.