I wonder how much of that is just lack of awareness. E.g., the whole story at [0] needn't have occurred if anyone involved were aware of VM emulation for older OS versions. But there's no money in selling old software, and Apple would probably open themselves up to lawsuits ("you told me to use a VM, and then it got hacked!") if they openly advertised it.

[0] https://news.ycombinator.com/item?id=35401895