There are some gags that don't let the drool out so much. My leather stuffer gag has a faceplate which covers the mouth and if it is tight enough does minimise the amount of drool that gets out (it still gets onto the gag and round your mouth but not all over the floor or the rest of your body).

A smaller gag may allow you to swallow easier while still being gagged. A larger one which is made of an absorbant material (i.e. sponge) will absorb the drool and stop it dripping. Its a case of finding the right one for you.

However, I agree... the purpose of the gag is to make the sub drool (and to muffle sound enough, and to humiliate and so on... )