Why would it be pointless for reptiles to sit on their eggs to incubate them as birds do?

reptiles are ectotherms and cannot raise their body temperature above that of the environment.
reptile eggs are not amniotic and have no shell, so sitting on them would crush them.
reptiles have no feathers and cannot cushion the eggs from bumping into each other without them.
reptiles have teeth with which to defend their eggs from predators, so they do not need to hide the eggs.