I know we have an Elder Scrolls Online forum, but this is concerning the entire series.

So, In Morrowind, Crossbows were a fairly popular weapon. No where near as exclusive as they were in Skyrim. The technology was seemingly lost for a couple hundred years as they were completely absent in Oblivion.

In the Newest Elder Scrolls online trailer, there are these mechanical bridge building harpoons that help the attackers storm where ever they are storming. Bear in mind the game takes place about 1000 years before Skyrim.

It seems like technology just kind of goes where it wants to in the Elder Scrolls universe.

Well, the Daedra seem to enjoy screwing with the mortals. Also, the Dragon Break could have had some unknown effects on siege machines. Then again, it could be (and most likely is) just based on the suspension of disbelief/creative oversight.

There is lore and there is gameplay. I think we just have to accept that gameplay is always going to take precedence over lore.