Noob question on telemetry

Sorry if this is a noob question. I was wondering why telemetry is being done at 915 Mhz and not in the 2.4 Ghz band. It seems to me if there is already a airlink up why not use it for telemetry as well? I have been playing around with some cheap quads and am about to build my first quad.

If you do not care if your telemetry interferes with your R/C transmitter control, then go ahead and use 2.4GHz for your telemetry.