As others have noted, this is probably mostly about branding. But that's why it is genius. Tim Cook is committing Apple to this pro-privacy position in a very p

As others have noted, this is probably mostly about branding. But that's why it is genius. Tim Cook is committing Apple to this pro-privacy position in a very public way. This means that a reversal of this position or a revelation that Apple has been acting contra it, would be extremely expensive to Apple's reputation with its customers, effectively costing the company a huge amount of money. By publicly committing Apple to this cause, Cook makes it more likely that internal teams at Apple as well as future versions of the company will adhere to this position. By defining a set of actions which, if made public, would ruin the company's brand, Cook makes it less likely Apple will take those actions.