It’s a matter of safety. In some cases, car seat protectors without anti-skid construction can cause child safety seats to slip and slide, compromising the seat’s full ability to protect. As a result, some experts are wary of anything that might come between the bottom of the seat and the vehicle seat it’s intended to fit. This is especially a concern in booster seats for older children, which are often held in place by weight and safety belts instead of LATCH anchors. If you want to use seat protectors along with child safety seats, be sure to look for seat protectors with an anti-skid design.