Unfortunately rankings don't determine fanbases. Rafa has more fans than Andy even if he is ranked 8 in the work and so more people who buy tickets for centre would want to watch Rafa rather than Andy. But I don't understand why Andy isn't on the 2nd court.
The problem is that these things become self-fulfilling. If you people players on a top court, the less engaged public presume they are the stars. If you put them on an outside court, the same people presume they aren't stars.
I wouldn't be surprised if there was pressure from sponsors to ensure their top players get the top courts, and Nike or IMG or whoever pestering the organisers. On top of that, Fed has admitted in an interview he would retire if he wasn't on the top show courts, so I dread to think what kind of fuss his people would kick up if they tried to demote him from Centre, and then there are his crazy fans! Not forgetting that tournament organisers and a lot of punters will be worried it's his last year.