An important difference here is that your shell script executes the steps in the order you defined. Make performs a topological sort on the required rules, so in the general case, a Makefile doesn't explicitly define the ordering of the steps, but instead the make runtime figures out an order on its own based on the dependencies.

The Makefile is a (default) goal and a sea of possible actions from which make creates a plan of action.

The shell script steps are manually ordered by the programmer.