I have a theory. I think it's because they're upset they won't be zombies. Reading the article would probably dispel my theory, so I think I'll just read the first paragraph and then let you read it. I like thoughts about zombies.
The entire body is as though agitated from the last movements of agony.
The last convulsions of horrid agony can, after thousands of years, still be seen.
For well over a century, the contorted features of ancient mummies have led to speculation of untold pain and horrible deaths. The examples quoted above are from the examination of Egyptian mummies more than 120 years ago.