Cadillac's ads (while very nice) are all about sports sedans carving twisty roads around the world. They're gunning for BMW, Mercedes, and Audi, and their ads reflect that.
But Cadillac remains all about that luxury. Mustard and mayonnaise. Drop tops. White people with gold chains. Basically any person with gold chains.
In short, anyone can get behind the idea of a big, classic Cadillac from punks to geriatrics and everyone in between. That's the message that you'll find in a rap video like this, and that you won't find in Caddy's marketing budget.
(Hat tip to Austinthebruiser!)