I'm not sure that would make sense across the board. For example, I live in Vermont close to the New Hampshire border. Other than grocery stores, most of our shopping needs are on the other side of the border. If they imposed restrictions on travel between states (which would be likely shot down on Constitutional grounds anyway), I and other people in my area (where COVID is almost non-existent) would need to drive across the state to the Burlington area fr shopping, which is the only region in the state that has needed to deal with outbreaks. Applied uniformally as a blunt tool, a blanket state travel ban could have some unintended consequences.