[p_ing]

There's no reason today's macOS couldn't support a Classic environment, like the early releases of OS X. There are a lot of support costs surrounding such an environment, so I don't blame Apple for dropping it.

It supports x86 emulation, for now.

I believe Windows has seen more architectures than Mac OS Classic and OS X combined.

Windows 3rd party software often drops support because Microsoft doesn't support the OS. It could be the desire to use new APIs that aren't included in 7/8 (or soon to be 10), but it's hard to support an operating system as an app vendor that the OS vendor doesn't support.

I always liked VMware's statement that they would support NT4 and above -- like, no you can't.

[microtonal]

* I believe Windows has seen more architectures than Mac OS Classic and OS X combined.*

I have never been a Windows user, but I used to keep an eye on it when NT was still the separate business version (pre-Vista) and my NT 4.0 (or was it 3.51?) CD-ROM had x86, MIPS, Alpha and maybe PowerPC support. When things weren’t as clear platform-wise, NT was really a multi-platform system. Since then also x86_64, IA64, ARM64.

[p_ing]

CE adds SH3 to the processor list.

[rjsw]

And ARM32.

[flomo]

Classic ran as suid root and was a big huge security hole on a multiuser OS. (which is probably why they got rid of it as soon as they could.) There are some more contained emulators of course.