In short it's about the actual forces on the pedal when operating normally, as opposed to what you note when it's frozen. Rather explaining the physics here I'll refer you to Google. Reverse pedal thread, left hand pedal thread, why bike pedal thread reversed, etc - any of those should work.

...and btw rotating the cranks rather than the wrench to both remove and install pedals is not lazy, but rather efficient. That's the way most shop mechanics do it.