Fairy has the same number of light moves as steel (dazzling gleam, light of ruin, and moonlight compared to mirror shot, flash cannon, and doom desire). The difference is that Fairy has other options (e.g. moonblast), but every special steel move is light-based. Whether the special side should override the physical side in type match-ups is up for debate, but I would use Steel for when a 'light-type' is thematic but unavailible (and I belive it has been used for both Jirachi and Solgaleo)If I have to argue it, while Steel as Luster Cannon, it is the only light-based attack of that type that I can think of (and maybe few more I have missed) while everythin else damaging is about hitting your opponent with chunk of steel (Iron Head, Iron Tail, etc), which is what Steel is good at in doing away Ice.
Fairy, however, does have more attacks themed around lights. Now this actually makes more sense if they make Ice resist Fairy.
Side note: other types with light based moves are grass (2, solarbeam and solarblade), normal (3, flash, spotlight and morning sun), ghost (1, moongeist beam) and psychic (3 or 5, luster purge, photon geyser, and prismatic laser, plus the possibility of light screen and reflect)