Well, first off, Apple isn't virtualizing Intel, they're emulating it. "Virtualization" implies that your CPU has special hardware support for running a kernel as if it were a regular OS process; which almost never crosses architecture boundaries. Apple does have special support in M1 for certain x86 features like total store order, but most of the work is done in software to translate binaries to ARM64 before they are executed. They just omitted emulating anything beyond Intel macOS user-mode, because that's relatively easy and lightweight[0].

Intel doesn't virtualize Apple hardware because it doesn't make business sense and is questionably legal (see also: Corellium). Apple silicon is just-different-enough from a regular ARM64 design that anything that can actually boot macOS almost certainly exists purely to break the macOS license agreement.

[0] Specifically, having all your code neatly packaged into executables and libraries means that you can AOT-compile nearly everything and not have to actually interpret or JIT x86 code. There's also no need to emulate, say, x86 context switches or page table walking; you just stop emulation, run the syscall on the ARM side, and then restart the emulation once that's done.

Of course, they still have a JIT, just in case you decide to run a binary that also contains a JIT.