I wonder why they have not done this already. Okay, Apple spends a lot of money with them, but would it be more than what they would gain from seeing a massive shortage of Apple devices and potentially a reduction in quality/performance?
Because Samsung is really, really big and the section they are suing is not the same as the one they are buying things from. It's doubtful that the section being sued has enough pull to make another section take a hit to their finances. Besides, having a good deal with Apple provides leverage they wouldn't have if they dropped it and no reason to believe that dropping it would give any other benefit besides being spiteful.