Technology

Well, "duplicate" functionality isn't counter, but generally it's not quite "duplicate" either.

cat doesn't do much, and technically in most cases where people use cat, they can skip the use of cat. cat and grep aren't at all redundant, but maybe you mean cat |grep , versus "grep file", but really the first form is not a design intent, it's that cat is a habit to "get content to screen" and "pipe to grep" is a habit to filter out whatever content was on screen.

cp and dd are not really the same. dd is meant to take specific blocks from one place and put them in a specific place in one other file. cp is about copying whole files only, and can do a bunch of files to one directory.

As to it being 'obsolete', well the thing is that UI design has been swinging back to "CLI-y" ways, because you only have so much real estate on screen for guided menu driven action, and a fairly open ended universe of things people want to do. When people use office, they usually just start typing what they want rather than trying to find it by navigating the ribbon.

Though the "one tool and do it well" usually doesn't happen in GUI land (closest I can think is NextStep had some of it, and vestigial bits of that are possible in macos, though never used), but it's still plenty valuable.