Hutch is an odd sort of fellow. Maybe Starsky had the poster, being more of a sports guy. Let's say one day Hutch is meditating at Starsky's house - because he meditates and he's always at Starsky's house, whatever. He comes down from his session, and he's feeling very universal and high and zen. And the first thing that catches his eyes when he opens them is this poster. And in his current state, he suddenly sees a certain poetry in it, he's compelled by the motion of the figure, he's almost moved to tears. He asks to have it, and Starsky lets him :D