The gaskets on side lights have served 2 purposes , one for a water seal where it needs to be , the second to cushion the edge of the hard trim from cutting the paint causing a rust .
Back in the 80's the Buick Somerset would cut into paint and rust at the bumper extensions that went into the fender . They were made out off a hard plastic material so the had edges . Not all did but most and can still be seen today on them . We removed them , smoothed them over and after repaint reinstalled them with great success .