The downside is twofold:
1. There is a limit on the number of official visits a team can use. With this car rental stuff, who knows if the NCAA will decide to extend probation through this recruiting cycle etc. (that's me speculating here)
2. If a kid is clearly not coming here, that is bad mojo for the kids who are here and legitimately on-the-fence. A 5-star kid telling you how great this and that is on your visit lessens some of that shine.
Bonus reason: Basing your argument on an outlier (DJ Williams) proves the point of those who believe the time and energy is better spent elsewhere. Richt is smart in the recruiting game, and is putting the time and energy on building the infrastructure first. The Dylan Moses' of the world need to actually show some interest before they get the time.