It seems very rational to assume bipedal motion is easy and fine control is difficult. Some babies can walk from 9 months. No 9 month olds are playing Beethoven's 5th on the Piano.
There was millions of years of very strong selective pressure making humans evolve to learn to walk easily. There has been very little selective pressure making humans be good at learning tic tac toe.
Often whether something seems difficult or easy to humans has more to do with how well evolution has prepared us for it than with the inherent difficulty of the problem.