Architecture compatibility is down to the manufacturers of the processors, not Microsoft. 16-bit was dropped in the x86 architecture and the only reason that Windows Vista/7 could support 16-bit applications was because it had an inbuilt subsystem for backwards compatibility which has since been dropped.
At this stage, comparatively few programs are designed for 64-bit, so there's literally no reasons to to kill 32-bit. Hell; most of the Windows 10 OS uses 32-bit services and applications, even if you get the 64-bit version.