>>19705719>>19705729This.
Coverage moves are used when your STAB moves are resisted. This is why Hidden Power can be used at all; a SE Hidden Power is weaker than a neutral STAB hit unless it's 4x SE or your STAB hit is resisted.
When you think of coverage moves, you want to cover as many types as your STAB is resisted by.
The few cases were Normal serves as the best coverage move is in the rare cases where the movepool literally has nothing else (Klingklang) and/or you're a physical mono-Grass type (Leafeon).
