Wizardry is Not Hereditary
The prime reason there are no dynasties of magic-users on the Coin is that the Talent for spellcraft, which is a rare gift to be born with, is an order of magnitude rarer in children born of parents who are magic-users, or who hang around magic-users on a regular basis (such as most royalty and their court magi). Areas of high background magic also seem to reduce the likelyhood that their inhabitants will be born with the Talent (while increasing the likelyhood of freakish mutations...).
Wizards Love Hats
universally across the Coin, those with the power to bend reality to their will like wearing some form of headgear, be is a traditional pointed hat, a horned helmet, a hood, a jeweled circlet, or a fez (fezzes are cool), even to the point of feeling quite uncomfortable when deprived of said accoutrement.
Wizards Can Fly
In addition to being able to cast spells that allow them to fulfill mankind's most ancient dream, the very process of learning magic makes a wizard exceptionally adept at thinking and navigating in a three-dimensional environment, whether it be on a broom, or at the helm of a skyship. Sadly, many of them are still utterly useless at navigating in two dimensions.