PHP Function warnings/errors suppressed - Why?

I noticed that the '@' symbol is being used to suppress errors about
missing functions in "siteaddsubmit.php" and a few other files. It's
in the code for posix stuff like posix_getpwuid() and
posix_getpwnam(). I've seen a few mailing list posts about blank pages
after submitting forms, this is certainly the cause of it. One could
use function_exists() to test but that seems unnecessary and the @'s
should just be dropped. Why are they there?

--Chris