If you can express your workflow as a set of dependencies (granted, not all workflows are easily expressed this way), make gives you parallel and incremental computation "for free".
Imagine that you needed to download a tar archive, unpack it, then run several simulations followed by regressions followed by figure plotting on the data. You could write a shell script to do this, but it would be hard to make the shell script simulate the capabilities of `make -j', and you'd have to do a lot of timestamping and file existence checking to simulate the incremental computation capabilities of make.
Imagine that you needed to download a tar archive, unpack it, then run several simulations followed by regressions followed by figure plotting on the data. You could write a shell script to do this, but it would be hard to make the shell script simulate the capabilities of `make -j', and you'd have to do a lot of timestamping and file existence checking to simulate the incremental computation capabilities of make.