Right . . . because drawing pictures on a piece of paper and having them move around with accurate physics is realistic.

I'm with Benson. If you want to self-impose a higher difficulty, then more power to you, but the fun for me lies less in trying to draw out a structure to get the ball to the goal before it hits the ground, than taking my time and putting together cool and elegant solutions (like catapults, trebuchets, levels and machinery).

Above all, it's a cool physics simulation. Bound yourself with arbitrary limitations if you want, but it's more fun for me making cool stuff.