Good question
skip! I never thought about it, but now that you bring it up...why didn't Legolas help more? Did he just look the other way when Boromir and Aragorn were toiling and breaking their backs and pretend he didn't hear them?
But like others have stated, Elves are very aloof - artsy, yet warriors in their own right. Tolkien's description of Legolas was actually a response to a reader who claimed Legolas was too feminine. Given that description, you would think Legolas wouldn't mind carrying a Hobbit down Caradhras. Maybe he thinks he is retired...being 1,000+ years old?!
Good question!