They might allow season ticket holders and skybox owners attend too.
The big fears would be having rioters buy tickets and make it inside the ballpark. AND in having a massive crowd try to exit into a disturbance. Locking out just the “general public” mitigates both those risks while still salvaging some revenue.
CNN:
Never before in the history of Major League Baseball has a game ever been played in a COMPLETELY EMPTY STADIUM...