Rubber Seat Spacers

Can someone give me some advice here. Over the years I have taken stuff on and off the car and these parts I somehow don't remember being there. I've seen in different companies that there are replacement rubber seat spacers that go under the bench seats of many cars, but I didn't have any on when I pulled my seat out. My car is a 70 Dart with a spit bench seat and will replace them if they are suppose to be there, but are they a necessity and do they do anything to seat height or comfort!!!!!!!!!!!!!!