Historically reptiles used to mean all sprawling or semi-erect amniotes. So all amniotes besides mammals and dinosaurs (which are erect)

Some people want it to be a monophyletic taxon, but all the relevant ones are already taken. They could have chosen that reptile means amniotes, but they choose sauropsids. In practice, reptile isn't used as a monophyletic taxon. When it is used, most people mean the historical definition.

Amniotes and sauropsids are already clear terms and don't need to be replaced.