The part you're overlooking is that NeXT was as attractive to Apple as it was because they had a series of high-profile failures to develop a replacement OS in

The part you're overlooking is that NeXT was as attractive to Apple as it was because they had a series of high-profile failures to develop a replacement OS in house. In Apple's case the re-write idea turned out horribly and the only reason they made it thru is because a former founder had created a startup years earlier and had a working OS that Apple could buy and use. Apple is hardly a poster child for re-writing software.