True, but it would likely take centuries of developement before they had a viable weapon - that's a considerable amount of time for a group to spend on a technology like this, when it largely proves to be unweildly and underwhelming. A lot of things are done "for the hell of it," but these are often dropped when they prove to be fruitless (or pursues in a non-serious manner).
The developement of real-world firearms started quite slow, but once it started to prove itself it became widespread and considerable efforts were put into pursuing this. However firearms had no real competition. In Tamriel magic is overpowering competition, so firearms would need to be extremely advanced before they were considered a viable alternative (in fact, it would likely require the developement of smokeless powder, something that showed up nearly a thousand years after the discovery of blackpowder). Since firearms presumably wouldn't be so widespread, due to competition from magic, I suspect this would slow their developement even more.
True, also early firearms that is before 1830 was very inaccurate and slow to load, it's estimated that if you took 200 trained archers with longbows against 200 with napoleon war muskets the archers would beat the crap out of the musketeers.
Why did muskets replace bows, muskets had better armor penetration however the main benefit is that it took years to train somebody to be good with an longbow but just weeks to use an musket well enough. So if you was able to make a lot of metal pipes it was simpler to raise large armies with musketeers, if they died you could conscript peasants and have more next month.
None of this apply in elder scroll, an large poorly trained army would have problem with area effect magic. real world example, nobody fight tight together anymore as bombs and artillery make it to easy to kill them all.
Now cannons was invented before muskets and would be useful in sieges, if you don't have magic to break down stone walls cannons might be useful, however it's not something the player would run into much, the canons would be to large and cumbersome to use against monsters like dragons.