I'm not so sure it is so useless. Consider when you want to "grep something access.log". Then you want to look at yesterday's so it's "grep something access.lo

I'm not so sure it is so useless. Consider when you want to "grep something access.log". Then you want to look at yesterday's so it's "grep something access.log.1". Then you want to look at the log before that, but it's compressed. "gunzip -c access.log.2.gz | grep something". (Ignore zgrep for the moment. Let's say I want to use grep's -A and -B options to show context of the lines that it finds.) To switch between the compressed and uncompressed files, you have to move the filename to a completely different part of the command, which requires more re-typing. You would have been better off starting with so-called "useless" cat. Separate out the concern of "putting a stream into the pipe" from "doing something with the stream". gunzip -c is just one command that might produce output.