I agree the chests are too big and don't really make sense as far as rarity and placement is concerned. It's another videogamey trope of "players have fun finding stuff" that ignores world building logic in a setting, and someone was just tasked with putting hidden chests all over the map.
And now everyone has to carry a shovel at all times. I just don't see the point. You can have hidden treasures without burying ridiculous oversized chests everywhere and forcing all adventuring parties to carry an extra item just for this. There can be loose floorboards, loose bricks, buried bags, hidden compartments in a drawer... It REALLY doesn't have to be comical oversized chests in illogical places that pop up like in cartoon. Again, a very children's game like design decision instead of one that would help craft Faerûn into a mature and believable setting.
