You know how, in old-fashioned superhero comic books, everybody's sentences always end in either a question mark or an exclamation mark? Never a full stop! It was originally done because the print quality of the comic pages was so bad, full stops didn't appear on the page! They continued doing it, even after print quality improved, because having every sentence end with an exclamation mark made the comic appear more exciting! Even when what was being said was actually rather bland!
Maybe the zombie exclamation mark is like this! It's there to make sitting in the cockpit seem more exciting! Even when you're just doing an A-B cargo milk run and haven't been interdicted in hours!