Pisses off existing crew already stuck in ME.
More importantly, there is no return of cash back into their own economies. This is a crucial aspect. In my way of thinking DXB is a giant real estate play, it's main export is itself. The more expat's cash it can capture in the place, the better as it generates demand for goods and services, and this enhances its value as tourist destination in it's own right. It is a closed loop system.
Having crew based outside DXB represents cash haemorrhaging from the system, rather than just the leak of savings as expat's move on elsewhere.
CurtainTwitcher is offline
The crux of it is the above mentioned Airlines don't have to deal with the reality of Industrial Laws in other Lands when keeping the minions in the ME and therefor basing will never happen.