Because the megaphone is really pretty bad.
Starting with the fact that the handle is broken off relatively quickly.
Followed by the unnatural use. You have just no gun button, but must while with one hand the megaphone considers it a turn on / off with the other. Or you can run it for simplicity and needs a lot of electricity.
The included microphone is of particularly bad quality. It almost falls apart from looking and the connector is only loosely in the book.