"cat - concatenate files and print on the standard output"
Cat has quite a few options that clearly deal with text files: --number-nonblank, --show-ends, --number, -show-tabs, --show-nonprinting, --squeeze-blank ...
BSD cat[1] is a little more conservative, but it's not entirely clear cut that when printing to standard output (or reading from standard input) you want binary mode. And silently copying a binary stream to a text stream does sound like a bug. Even if that is the expected behaviour of standard "cat".
