"Gauge" is normally understood as "mathematically redundant" Why are gauge theories so prevalent? Why do they always seem to win out in the contest to describe the world? In a theory with some group of gauge symmetries, only the gauge-invariant quantities are considered physically meaningful. But the mathematics that people find most convenient or true to nature allows for other, gauge-dependent quantities and these are considered physically insignificant redundancy. So why not refine the math so as to eliminate all that meaningless "filler"? Isn't it inefficient, just "extra baggage" diluting the real physical content of the theory? But no: the successful theories are always gauge theories. Why is that?