Playing devil's advocate regarding "retro reps not existing," the existence of a token spot for both retro and shock/hardware newcomers is an understandable jump to take when, conveniently enough, exactly one newcomer per game since Melee can fit into both labels (ICs/GW, Pit/ROB, DHD/WFT).
Beyond that, most if not all of those choices seemingly came about as a result of Sakurai singling out a subset of characters from whom to choose a single candidate (with the ICs famously beating out Balloon Fighter/Urban Champ/Excitebiker). I don't buy for a second, for example, that WFT, a non-character for all intents and purposes, was brainstormed up in the same session as Mega Man and Little Mac, rather than from a list of "surprising" options.
"Reps" are awful, I agree, but this is one area where the principle may actually apply.