Specifically it's because Apple likes to take the Research and Experimentation Tax Credit for operating system development. The R&E credit requires that you work on a new product and not on simple refinement of an existing product and its features. There are a lot of subjective factors involved in qualifying and Apple felt more secure by requiring some money to upgrade. The big advantage was not the income but the big fat check from the federal government at the end of the year.
The R&E credit is a pork barrel scam for big companies with clever accounting departments, of course. But if it's there, why not take it?
"In 1996, 1999 and 2000, for instance, the California Legislature increased the state’s research and development tax credit, permitting hundreds of companies, including Apple, to avoid billions in state taxes, according to legislative analysts. Apple has reported tax savings of $412 million from research and development credits of all sorts since 1996."
$412M on the hundreds of billions Apple has earned since 1996 are pennies. That doesn't seem that much... Are there more?
