actually, there is a "standard" of sorts, its 22 gauge wire.
the wires you find in those 2 or 4 conductor pups, those are really THIN. Even if you put the arguement of tone OUT of the equation, its size makes it too fragile anyway.
And yeah, the tone thing is apparently very real. Better wires = better tone... Mr Beez can hear a difference when he uses his special wires in his soldering jobs, cna't rem what they are... like $50 a meter or something.