i just like when the rear wheels dont look sunk in and usually they will if the front are setup right and you buy rear ones to match. You end up with the front looking good but the rear look bad. Spacers just fix that one issue by pushing the rear out where they should go.
I needed wider rear rims and the front cant take more than 9 wide stock so I didnt have a choice
but I wanted 8 wide in the front