Iraq isn't just a big desert, its a country that supports tens of millions of people and has the oldest civilisation in the world. There is desert in the west, a broad fertile centeral valley of the Tigris and Euphrates and mountains in the northeast.
And again, dispersal isn't the be all and end all, planes don't run primary missions from roads etc. they are used as part of a shuttle; load up from main base, land at dispersal road/minor airfield for top up with fuel, ground loiter for a few hours, fly mission and return to main base. If planes are having serviceability problems they don't disperse, only trouble-free planes disperse. It's just a way of increasing the percentages.
And again, dispersal isn't the be all and end all, planes don't run primary missions from roads etc. they are used as part of a shuttle; load up from main base, land at dispersal road/minor airfield for top up with fuel, ground loiter for a few hours, fly mission and return to main base. If planes are having serviceability problems they don't disperse, only trouble-free planes disperse. It's just a way of increasing the percentages.