OK, the Unix philosophy holds that this is one of the most important things, and therefore it's easy to do in shell.

But what if it's not? It's perfectly easy to write code to do the same thing in a programming language without invoking any other executables, let alone piping the output of one into the input of another. So the claim that this functionality is what makes Unix and shell scripting effective is vacuous. They are good at doing something which would not be necessary if one was not using them.

Being able to compose programs is not a necessity, but it saves effort. A single pipe replaces M*N different programs with M+N different programs. This is how Unix won.