Why do some people use postscripts in emails?

The historical function of a postscript was to allow someone to include information that for one reason or another was missing from the body of a letter without having to rewrite the whole thing. In the age of email, however, we do not face such problems. It is an entirely trivial matter to go back and fit the information into the body of our message. Why, then, do some people still use postscripts?

P.S. Just in case you don’t know, this is a postscript. That’s what “P.S.” stands for in this context.