And that fits history, so it is easily understood.
Muskets arent as good a weapon as almost any war bow. They just arent. In any way.
But they are trainable in hours rather than years, and can be made into a reasonably effective spear for when an enemy closes, while bowmen need to carry secondary weapons.
Which not only means that you can field entire armies with muskets as opposed to separate archers and formation combatants, it also means that you can spend years training a combatant to do a bunch of other stuff on top of shooting accurately, to much greater degree, even if they didnt grow up with it.
Muskets kinda suck, until you are fielding an army, and then they are fantastic.
In most fantasy settings, including dnd, even Eberron, bowmen are much more common than spellcasters.