It's not car racism. In college I worked valet for 3 years on weekends. The cars in the front are front spots. The front man (guy who doesn't run to get cars, just hands tickets and keys), makes money this way. First it's a way to draw attention to the restaurant or club. You charge extra say $100 or more to keep the car up front if the owner doesn't want it driven. On busy weekends such as new years or other holidays the front guys would make about 500+ bucks in extra cash just from front spots.
If the parking authority comes by and wants you to move it you risk getting a ticket which the boss won't pay for so that's why you charge extra money. Athletes like Ryan Howard and football players would come in and ask me to keep the car close. If they didn't pay what we asked then we would keep it up front for as long as we could, park it and then bring it back up front at the end of the night before they come out.
It's the quickest way for the front guy to make extra bucks because they are responsible for tipping the runners. I loved being a front guy when others were absent. I'd make about $100+ in tips every night from people with nice cars who wanted them parked out front.
It was fun and I got to drive pretty much every car made up until I quit, from beat up Fords that died once you got to the garage to the lamborghini diablo, Ferraris, etc. The best part was when the parking authority would start walking around we would hop in and take the cars out for a spin around the block and then back up front.