Part of this is also the need to actually defend your trademarks. As cited by several people above with the precedent of Raspberry and Blackberry, etc, it's clear that not trying to enforce your trademarks makes enforcing them later more difficult.
I suspect Apple didn't really expect to win and didn't care if it did - it just defended its trademark in order to keep its strength and to set a strong precedent for the future.
And, if you're an Apple lawyer* then it behooves you to defend that trademark to the very best of your ability.
Not that this isn't somewhat thuggish behaviour, just that it's not legally unwarranted.
* - I am reminded of Disaster Area 'research accountants'?
Biting the hand that feeds IT
