[jroseattle]

Apple has/had a history of re-writing code over the years. The first iPods and their iterations were code re-writes, IIRC. Many of the onboard applications were completely re-written for the iPad.

[Daishiman]

Rewriting for new hardware is totally different from rewriting business logic. In the first case there are sometimes no other choices left.

Also, the code that usually goes into hardware microcode and firmwares is much more tightly coupled.