Why do Freemason's always step off with the left foot in masonic ritual?

This would be in deference to the Egyptians, to which much of their culture is based in. This is especially in respect for Thoth (Tehuti) who is the bringer of wisdom and knowledge.

As intriguing as that answer is, left-footedness is not particularly Masonic or Egyptian. The assumption of the question is flawed, and the answer is based on an equally flawed assumption.