When using either /setblock or /fill, and you're placing a powered redstone item, such as a lit redstone lamp, it will automatically unpower itself after its normal game tick delay. I 100% understand if this is seen as Working as Intended, but consider this. If it's placed as that value, that means said player wants it like that. Perhaps they want a ceiling light for a map that has no way of being otherwise being powered, and they don't want to lag the game with repeating command blocks to make them that way. The way I see it, they should only turn off if they're updated with an active redstone power source.