Theory and Practice

What prevents you from leveling up Swiftness or Nobility? Finding a staff or a scroll with a combat spell has a high probability on any map (I would even say a very high one), and you don't need to spend experience on magic; instead, you can level up what's available in universities or on altars.

Um... well, the thing is, it requires a lot of skill points.
A staff isn't that easy to find. Since we won't be leveling up magic, a simple fire or ice bolt spell will be very weak on its own, so you need to find a staff... at least one with fireballs (although that's still weak), and even a scroll with lightning. And with the huge variety of scrolls, it's not that easy to find exactly what you need.
You can't level up magic beyond the second circle in universities, and with altars... well, even with the best-case scenario with universities, you need 2 altars to reach level 3, and then... it's a lot, in general.

I agree about dispel and cancel, but again... if you find a scroll ;) So, if you're going to level up a Guildmaster, you need to be at least 80-90% sure that you'll find the necessary spells along the way