No, it is a fact. You can have a smooth criminal cleric. A greedy charlatan paladin. A prideful barbarian scholar (NERD RAGE!).
The backstories are very connected to their classes though. Gale for example, is more than just a prideful scholar, he is intimately connected to the Weave and chosen by Mystra the goddess of magic. Hardly makes sense for a fighter to be the consort of the goddess of magic and experiment with Netherese magic.
He could easily be a paladin of mystra/azuth, a cleric of mystra/azuth, a sorcerer, an eldritch knight, a bard, an arcane trickster, etc. Moreover, if you would get so butthurt about swapping his class... dont? I'm not sure what it matters to you if someone else changes their Gale in their playthrough. Or do you simply have to dictate their tastes as well as your own?