There are several benefits to it. "cat filename" is a natural starting point for building pipelines interactively one step at a time. It puts the first input o

There are several benefits to it. "cat filename" is a natural starting point for building pipelines interactively one step at a time. It puts the first input on the left side of the command that consumes it. (The alternative of "cmd1 [<]filename | cmd2 ..." does not quite read left-to-right, and some shells do not support "<filename cmd1 | cmd2 ..."; for example, fish doesn't.) When you are done with preliminary testing and want to run the pipeline on a larger amount of data "cat" is quicker to replace with "pv" (and vice versa). You do incur a performance cost with both "cat" and "pv". The command consuming the input also can't seek on it with "cat", but it doesn't matter if you are processing the input one record at a time. If you like the ergonomic benefits, use "cat" until you are optimizing for performance.