One has to ask: how often, compared with simply listing a file? Being very picky (and off-topic),
catdoesn't actually concatenate files unless the output is directed to a file... so really it is just reading all the files in the list and sending their contents to a standard stream.
yup, and that's why it was called concatenate, which means linking things together. In this sense, sending all the files given on the cmdline (even if just one file) to stdout, linked together (i.e. one after the other with no break), whether or not that "standard output" is redirected to a file, or the terminal (which is also a file, as noted above).
catwill also stream its input, if no files (or the file "-") are on the cmdline.
that said, I agree it's an odd choice of name! But after 35 years, I've got used to it
what did DOS use?