Following the thread of my previous analysis:
In most of the Merlin fics they make the kingdoms surrounding Camelot anti-magic for maintaining diplomatic relations with Camelot Except for one of the most problematic kingdoms, that of Cenred, where sorcerers are enslaved for warlike purposes.
Let's be honest, we're talking about royalty, the rich stay rich by preventing others to become rich.
In this case let's not talk about money, let's talk about power
What differentiates the "blue blood" from the common man/woman?
If you were a peasant in medieval times you probably wouldn't even have the time to ask yourself these questions because you would be busy cooking a meal that takes all day to make; Taking care of the few cattle from which you get sustenance, or working as a donkey. But if magic were free, popular knowledge and free of stigma, you would not only have a lot of time.
YOU WOULD START TO ASK YOURSELF QUESTIONS
Historically in fact, "magic" has been hated precisely for distancing the citizen from social/religious norms.
In a world where magic granted you the unimaginable, absolute power that made dreams achievable; anyone would begin to wonder what makes these self-appointed "chosen by God" really so special?
That's the point. Power is power because it's centralized, because it stands out, because it offers you something you can't get on your own.
Royalty is supposed to provide a certain sense of security to the people (in medieval times). Would this be enough for a people who feel they can stand on their own two feet? A dissatisfied people?
The royalty of Merlin's world could not allow such questions, there is a reason that I have not read in any fic until now.