April Fools Day is recognized as a holiday off from work/school in Gotham as a preemptive measure against Joker. It’s easy to blow up a skyscraper or a school. Not as easy to target thousands of individual houses. April Fools Day is treated like the purge and everyone hides out in their houses. No one answers their doors. No one even answers the phones. Gotham on April Fools is a ghost town.

Joker always finds a way though.