Let me put it another way then. A Fighter usually comes from humble beginnings and has an innate affinity for the martial arts, a Knight is a noble who has been trained from a young age in those same arts. From a visual perspective both classes are identical. They both use Swords and shields, they both wear armour. and they both use hack and slash animations. Where's the difference from a gameplay perspective? I'm using these because they're the martial analogues to the Sorcerer and Wizard.
Your comparison isn't valid. Both fighter and knight would need some training and would be able to control their martial art abilities. While a Sorcereer and a Wizard are more like a fish and a human who learned to swim. The first one would swim just because that's how it lives, and the second one can leave this kind of occupation entirely. So returning from comparisons to game mechanics: Sorcerers are well known for spontaneous spellcasting and effects till narrative "my sorcerer just accidently puked with a fireball", plus they have some effects coming from their ancestry.
