I try to keep logic with my fantasy world-building, giving reasons as to why things are the way they are and expanding on lore.
A quick example, the Grey Continent, home to vampires, is near the equator. For that reason, it would be mostly sunny and a hellish life for vampires. and for that, a simple reason to combat it with real fantasy world effects is that a weather mage created an unending cloud covering the entire continent, shielding them from the UV rays.
Because of this, mage towers have more depth and reason behind their existence. They focus on assessing the weather and climate, among other things, just beyond the typical place for mages to study, because how can you just study for your lifetime without a job or a benefit to society?