You are right, 100 homes and it is a large event.

People forget to account for the logistics of moving large numbers of people.
Most of our cities are so large and dense that they are almost impossible to order evacuated.
When you try to imagine a large scale evac don't just jump one order of magnitude, jump at least 2.
100 homes is only one large apartment block, a thousand homes is 10 or 20 of them.
Think of at least 10 thousand homes.
Then think of at least a million people needing to move instead of 3 or 4 hundred.
Then look at the size of cities like L.A., New York or New Orleans, and their everyday traffic problems.

Not only is there no way to round up and herd that many people, there is no path to herd them down, or place to herd them to.

This is another reason to leave the theatre early if you have advanced notice.