Whitepaper: https://cdrdv2-public.intel.com/776648/x86s-EAS-v1-4-17-23-1.pdf
Basically, “Get rid of all the real mode and 32 bit mode cruft nobody uses anymore.”
It keeps the ability to run 32-bit userspace applications.
Seems reasonable to me. It’s more or less what ARM has done with AArch64 processors that still support AArch32 EL0 execution.