You are so right, it's 'asked'...... it's 'asked'........ it's bloody 'asked'.
What sense does 'arsed' make................none at all.
'I can't be arsed' may be a phrase NOW, but that's only because the thread was promolgated by some moron with cloth ears who 'couldn't be asked' to think why what he THOUGHT that he'd heard one of his mates say was nonsense. Or else he didn't want to appear a jerk by asking his mate what the hell he was talking about.
It puts me in mind of the story of a little lad who had learnt the Lords prayer at school 'parrot fashion' and later took an awful lot of convincing that the words were "Hallowed be thy name" and not (as he thought) "Hallo Beehive Lane" or indeed my son who thought that the Fat Controller (from Thomas the Tank Engine) was really called "The Fact Controller".
So yeah if you're aurally challenged, or the Offspring of someone who is aurally challenged, or else someone who just can't be asked to stop and think what the hell it is that your saying, then I guess that the phrase 'can't be arsed' makes a lot of sense. For the rest of us..........Oh I just can't be asked.