But a bow and an arrow and a bridge are fairly mundane things, and don't require an awful lot of jumps in technology for them to exist. Steam power and gunpowder and such, on the other hand, do. And you won't get these jumps in technology if you don't have people researching them and investigating them. In a world where you can summon a fireball, a bit of powder that explodes when lit isn't really a big deal, because you can already make an explosion anyway. Similarly, you aren't going to get anyone interested in surgery and such when you can just cast a Restore Health spell etc.
I understand where you're coming from, but if we had a source of energy like they do in Nirn, we would not have cars and guns. Everything that exists comes from old ideas and improvements to them, along with a couple of genuine innovations, but you would never have got to the stage of an industrial revolution because you could just automate everything with magic.
Ok. I'm not being clear. I'm sort of responding to two different kinds of settings. A setting in which magic is commonplace, and a setting where magic is rare.
In a low-magic setting, technology will advance quicker than in a high-magic setting.
In a low magic setting, there is good reason to investigate weapons and armor. That need is less when you already have something to do that (magic).
I imagine a setting in which the non-magical people are in an
arms race with other magical and non-magical people. You will always be looking to outdo your competition. This applies to economics, politics, science and various other fields.
Innovation comes from necessity, but wouldn't the drive to be the best or outdo competition be as much of a catalyst?
If the fighters guild fought the mages guild, you would see the warriors looking for ways to outdo their magical foes. This means they need to figure out how to fight fire with fire. The mages on the other hand will no doubt seek further magical powers because that is there forte.
So maybe I wasn't doing a good job distinguishing between a high-magic setting and a low-magic setting.