No matter how technically correct that may be people just don't like doing work for some theoretical future benefit that may never materialize. Supporting 32-bit imposes a cost I have to pay right now today for the benefit of very few people (and a shrinking pool at that). Why not spend the effort on something more productive?

It is also likely that general purpose CPUs will use 64-bit integer registers and address spaces for the rest of our lifetimes. Computing has already (for the most part) converged on a standard: Von Neumann architecture, 8-bit bytes, two's complement integers, IEEE floating point, little-endian. The number of oddballs has dramatically decreased over the past few decades and the non-conforming CPUs manufactured every year are already a rounding error.

FWIW If a transition is ever made to 128-bit that will be the last. There aren't 128-bits worth of atoms in the visible universe.