My friend was recently caught shoplifting while i was with him, why is it we both have to pay the $150 fine?

While i was with my friend he was shoplifting from a department store, i knew he was doing this, but never once touched any of the merchandise, let alone stole any of it...long story short, the loss prevention officer got us and took us both in. Luckily we didn't have the cops called on us, but we were both forced to pay a $150 fine. Apparently i was the "accomplice" and therefore (to him) i am also guilty. I think this is bull ****, but its better than having the cops on me...do i really have to pay this fine?