I once too was "Well the RAC is great, whats wrong with it". The problem is that the basketball teams do not have 24/7 access and have to share the space with other teams that need to use it. Those teams deserve a place to practice as well. Nobody wants to take away the limited space that other teams have, that just makes no sense.
The thing is, basketball is the main sport at Mason, so in order to show to anyone who may come (donors, recruits, fans whatever), "Hey we want BASKETBALL to be great", they have to have preferential treatment in terms of the fact they can have resources whenever they want, whether its shooting, scouting, or whatever. They currently don't have that.
The RAC is a great facility and I'm sure athletes get plenty of resources, but because basketball is the focal point of the athletics program, the main program and money maker, they need the extra care to be there. Plus with basketball having their own space, they won't take away from other teams who need the limited space. In addition, since many other conference schools have great facilities and resources, Mason needs to be able to keep up, over the long haul it will yield dividends.
The new area for basketball will probably also be open to students and others when the basketball team isn't using it.
I personally can't wait for the facility to open.