No one else is using rear covers and some people didn't like the look of them or understand the reason for them. Unless there is a groundswell of interest in them or other companies start to use them Honda is unlikely to try them on a car meant to appeal to the masses.
It is not apparent but what Honda did on this concept was to put clear smooth plastic covers over the deep cut chrome like wheels. This would smooth the airflow like rear wheel covers. Unfortunately this would also collect water and dirt in real world conditions. Soon you would have a miniature eco system evolving "under the glass".
As a child my miniature cast metal Hudson with rear wheel covers was a prized possession. ( It still is.) I think the covers look very classy on the Insight too.