Because it's my understanding that Mac OS couldn't handle multithreading and that even if it could, that was only something you got if you owned an 8600 or 9500/9600 with an MP processor chip.
That's not true. Take a look at the ThreadManager extension, which was released around the time of System 7.5, IIRC.
Also, OS 8.6 introduced a nanokernel with threading support built-in.
Was m68k a MP-capable design?
People were running Unix on the 68000 in the 1980's.
