@Greg Bird
"from what I understand of US law if the patent owner doesn't vigorously defend a patent and it becomes ubiquitous then they essentially give up the right to the patent"
You're thinking of trademarks, not patents but these are aren't actually patent claims from Apple but something halfway between patent and trademark. But no, they don't need proactively defending to survive.
It's actually common practice to *not* assert patents while waiting for others to adopt them, so called submarine patents you only spring when enough people are infringing.
In fact it's usually a very bad idea in the US to actually reach court with patent disputes because it's the leading way to lose your patent. In software 90% or are lost and Apple's design patents are so weak they're unlikely to survive this trip to court. Lose the patent and you can't get anyone to volunteer licence fees.
So why did Apple go this far? Simple, if they backed down those injunctions would vanish in short order. Going to court hurts Samsung a lot, win or lose.
It also keeps alive the illusion of threat from Apple, something few in the industry seem to take seriously at all even with Apple on the warpath. It would vanish completely if they quit.