Specific to Elder Scrolls, but applicable in any high fantasy milieu; by user AndrewJamesDrake:
“There’s a problem with that: Someone needs to Invent the Gun before someone else can pick it up. The Economics of Tamriel make this avenue of research unattractive.
The Natural Talent and Skillset required to perform Engineering and Scientific Research has a significant overlap with the Natural Talent and Skillset required to become a Mage. This problem is compounded by the fact that Magical Research has very little applications outside of Magic, since Mages are overriding the Laws of Physics instead of working with them.
Since Mages are known to be useful, people with the aptitude for Magic are pushed towards that vocation. That means that there’s not a large population of people doing Normal Science that could be used to create Useful Technology. This makes it way harder for the Gun to be invented… and that problem is compounded by a lack of funding.
There are (Primitive) Grenades and Cannons in Tamriel. They’re known technologies. However, they’ve never seen Large-Scale Application in Warfare due to Economic and Strategic concerns.
The Economic concern is the complex supply-chain necessary to equip soldiers with Grenades, or to support an army with Cannons. You need to manufacture and transport Grenade Shells, Fuses, and Black Powder to equip your men with Grenades. You need to manufacture and transport Black Powder, Fuses, Cannons, Cleaning Equipment, and Replacement Parts for Cannons to field them. Grenades and Cannons also require wagons, pack animals, and engineers to assemble them (and operate the Cannons) to be effective in the field.
Incidentally, those Engineers are probably intelligent enough to be trained as Mages… which means that you’re giving up Mages in exchange for allowing your men to throw Grenades that could then be thrown back to them or blow up in their hands because the burn-time of fuses is really hard to predict. Fireballs don’t have that problem. This opportunity cost needs to be factored in.
The Strategic concern is the storage of Black Powder in a world where a Mage can cast Invisibility and Muffle, sneak into your camp, and then put down a Fire Rune inside the tent-flap. Alternatively, for most of Tamriel’s History, they could just cast Fireball on the powder-tent and then use the Mark and Recall Spell to get out with their life. Your Supplies are incredibly vulnerable to sabotage that’s incredibly difficult to stop. You’ll need to have Mages on duty 24/7 using the Life Detection Spell to try and catch an infiltrator.
Incidentally: That adds another cost to fielding Gunpowder Weapons. You’re going to have a few Mages unable to join battle or do something more useful because they’re needed for simple guard duty.
That issue can be mitigated by Enchanting the Barrels… but that just adds a ton more expenses to fielding Gunpowder Weapons since you now need experienced Enchanters to layer Fire Resistance Enchantments on a Barrel… and you need to provide them with Soul Gems containing fairly powerful Souls to provide the Gunpowder with enough protection to avoid a cascade of barrels setting each-other off.
By comparison, Mages can do everything a Grenade or a Cannon can do… and they can do it with Lightning and Ice as well as Fire and Force. They’re uncommon, but not rare. More importantly: They can do more than just Destruction Spells. Illusion Mages can fuck up the enemy ranks, or gather information. Restoration Mages can get your people back on their feet in minutes… or Ward off hostile Mages. Alteration Mages can allow units to breathe water, enabling some insane flanking maneuvers, and can use Telekinesis to hurl heavy objects at high speeds. Conjuration Mages can unleash Daedra on the enemy army. The Expanded Utility of a Mage makes them inherently more valuable than a Cannon.
Most Importantly: The Supply-Chain to support a mage is the same one required to support a normal soldier. Strictly speaking, all they need is time to recharge their abilities, instead of being dependent on a complex supply-chain. If you rotate your Mages, like you rotate normal soldiers to deal with fatigue, you can keep a Spell Barrage going all day long. At most, your army might have its foragers gather the reagents for Magicka Potions while they’re out foraging for food. By comparison, Cannons and Grenades become dead weight if there’s a supply shortage at any point. .
Gunpowder Weapons just don’t provide enough of an Advantage over Mages to justify burdening an Army with the increased costs. That means that there’s not money going into researching how to make better cannons (that money is instead going into Magical Research). The ones we have are early cannons… which have a tendency to explode when mishandled (or due to construction flaws/wear and tear). Until those issues are solved… building a man-portable cannon (a gun) is going to be impossible.”