Glass jars aren't reused because of the infrastructure required to reuse them. The only glass I can think of which is reused outside of the point of sale are soda and beer bottles, and that is only usually at restaurants which will collect the bottles they use to ship back.
Outside of a massive sorting facility in every supermarket generating no value for the store owner, the only other way to ensure bottle reuse would be subscription delivery like milk used to be or hyper focused stores which only sell a few products like how grocery shopping used to be.