Those are leaf galls. They are abnormal growths that form typically from some sort of insect irritation (but can also be bacterial or viral). While unsightly, they are harmless.

You can't prevent them from occurring and they will remain present until the leaves drop in fall.

"Galls on maples appear sporadically and do mostly cosmetic damage. The threat to the health of the tree is negligible or limited. Treatment is rarely justified. Because eriophyid gall mites crawl to the bark to spend the winter, trees could then be sprayed to suppress the mites there. By waiting until the leaves have fallen, it is easier to cover the bark thoroughly and much less pesticide will be needed."

NC State Extension Publication

If a plant breeder marketed a Maple with pretty pink bobbles I’m sure people would rush out and buy it. I wouldn’t waste time or money trying to get rid of the galls.