It is not the Sahara, but the possibility that there isn't any interesting until the GUT scale. On the Wikipedia, I've read:
"The attraction of a desert is that, in such a scenario, measurements of TeV scale physics at the near-future colliders LHC and ILC will allow extrapolation all the way up to the GUT scale."
Consider we have the negative information, i.e. somehow we would know, or we could suspect with a quite high propability, that there is really nothing until the GUT scale. Could be this negative information also useful? If yes, how?