I don't get people who look at a Pokemon and think "I think a Pokemon should have a typing that makes it fundamentally worse because it makes sense."
Exibit A: Lugia being part water type. You just gave it a 4x weakness to one of the creatures it meant to command (Zapdos). And do you really want a legendary Pokemon to share a type with PELIPPER? Besides, now you just have to deal with the fact it barely has any water moves to begin with.
Exhibit B: The Flabebe line is WEARING flowers, they ARE NOT flowers. Are you going to give this thing a weakness to fire, ice, flying, a 4x weakness to poison, and a weakness to bug just because you think having any sort of plant = grass type?
Exhibit C: Electric / Dark Luxray... Why? The only benefit is that it gets STAB Crunch. Now it's weak to fighting, fairy and bug. It had only one weakness before, and now you're giving a Pokemon not known for being a defensive wall... three more weaknesses for the "aesthetic?"