Because prior to a few updates ago, any 1st level newbie could talk to Garent and get that quest....and most of us did.
Too bad that quest would usually shred most people into confetti and was way too difficult for the amount of reward given. So, if memory serves, the quest became one like Moraken's where you had to be 10th level before you could get it.
So a lot of people have the quest in their journals from before AND have enough character levels, but head or no, Garent won't even talk to us.