The Lucky Egg isn't really as useful, in my opinion, before Generation V, but when I was trying to complete my Pokedex in HeartGold, I actively tried to look for one to help me evolve a Pokemon I needed a Pokedex entry for. After Generation V, though, yup, very useful item, especially since it's just given to you by the professor. It's amazing how rare the item was back then, and now it's literally just given to like candy in newer gens.