The biggie is it's size. I see them for sale (tho people want a ****** fortune for them) once in a while, and while sure they're big, and, well, big... unless you own a huge shop, where are you going to put it?
It's like those "service walls" they used to have in dealership (and some independent) shops... Yeah, they're nice, but unless you got the real estate to put it, it's tough. Plus, back to back, they're 5' plus - so between service bays, you're cramping your workspace.
And finally - unless they're in a color you (or worse, your service manager) can look at for the next 10+ years, you're stuck with it as a permanent fixture. Want to sell it? Good luck. The shop decides that bright green doesn't go with their "brand"? Mmmm.... could be an issue.