It opens air flow
A main factor in recurrent ear
infections is the build up of thickened mucous in the middle ear. This weeps off the walls of the space and should flow thru the eustacion tube to your throat.
Recurrent infection may thicken the mucous & if it never flows out, germs love it. The tubes provide a window in the ear drum so air can get in & mucous can drain out. With the mucous is gone, no food for germs.