When the door skin is pulled off the front doors, is the the white clear plastic needed? What purpose does it serve?

 

should be a vapor barrier, keeps the electric buttons and other interior stuff protected from moisture. If it wasn't needed car manufacturers wouldn't waste their money on it. It probably won't destroy your car if you take it off... but try to keep it intact for a daily driver.

 

i didnt see any white plastic when i recently put in some jdm itr door panels...and i'm the first owner...thats weird.