I think the goal here is to show that the quantum computer is not just a complicated classical computer. To do this, you design a problem that should be "easy" on your quantum computer but exceptionally hard (practically impossible) on a classical computer.
Compare this to, for example, D-Wave. As far as I understand their quantum computer they could show it was faster but it was "X times faster" rather than scaling in a completely different way.
Compare this to, for example, D-Wave. As far as I understand their quantum computer they could show it was faster but it was "X times faster" rather than scaling in a completely different way.