I noticed that the battery for the motor runs the servos too. Why would i need the 4 aaa batts for the reciver? Or is it for gliders and thermal planes? would like to litein the load if poss.

I'm not sure what plane-radio-motor combo that you may be using but in general you don't need the extra battery power for the receiver if you already have a motor battery BUT I’D NEVER (well almost never) try to fly a plane w/o a separate power source (Rx battery).

If you have just a single battery pack and the motor uses up all its juice you have no way to steer your airplane down for a dead-stick landing. No Tx battery power = no way to power the servos and this could (and probably would) result in your increasing your stock of balsa wood along with the elimination of one air-worthy model from your collection.
This can be an expensive method of lightening one’s model.

I suppose you might get away with this if you kept your flight times very short and always checked the charge before another flight (which is a good idea anyway!) but beware- its pretty risky.

Most of the electric models don't need the RX battery pack. The modern electronic speed controls have a motor power cut-off that kills the motor while you've still got enough battery to bring the plane down safely.

Read the instruction manuals for your ESC, and for your model. You'll probably find that the AAA pack can be left out with no problem at all. If this was a package deal, the RX battery holder was probably included just so you'd have it in case you used the radio in a plane that wasn't using the electric drive ystem.