For me is a matter of wasted space. In a sports car, space is already at a premium. Add in a USACi quality install and it's REALLY at a premium.
I'm having my dash customer fiberglassed to house my Xenarc and Alpine head unit. Since I'll have basically a huge chunk of free space behind the monitor it only makes sense to use it as computer space. The drives will be mounted externally, either below the dash or in the glovebox. But the solid state will be held behind the monitor.