Because it's a CPU from 1978 (complete with a tiny register file, lack of orthogonality between the registers, and horribly awkward addressing scheme) that's been progressively kludged up into a modern processor, and even on the new models you can still see the surgery scars. 68k was a pleasant 32-bit architecture right from the get-go.
The 68000 was a CPU from 1979 but by 1996 the 68060 was effectively dead as a desktop CPU.
Just because it didn't live long enough to have kludges doesn't make it worth using for more than retro computing today.
I'll agree that the design of 68k was better, but that doesn't help me in any way today, where it actually matters.
This thread is nothing more than nostalgia vs. logic and it's degrading fast.