what's the point of FP if processors are still Von Neumann?

You are shooting yourself in the foot by thinking in a manner inconsistent with the computer.

The Von Neumann architecture is a poor approximation of computer science from the days when bit flips were an actual mechanism physically being flipped around.
``Computer'' was coined to refer to a human with a degree in mathematics performing computations, and I am pretty sure they didn't come with BIOS or a front-side bus.
Functional programming is the application of computer science. All other programming is a bit-flipping compromise.