What they "need to do"? Why did Apple need to sue Samsung? Apple doesn't need the cash, Samsung's tablets aren't hurting iPad sales very much, and Samsung didn't show any inclination to pre-emptively sue Apple.
If you don't enforce your patents there isn't much point to having a patent.
It has less to do with sales. The whole patent suit situation is systemic to the patent system. That and Apple tends to get into the news often it becomes "newsworthy" enough to report.
