Early on in his career, in the Hedge, he has made the mistake of mentioning he is a wizard. He has since been unable to shed this mask. By now he is way past the point where attempting to maintain cordial relationships induces less risk of angering the Fair Folk than ignoring them.

On the other hand being a wizard means you are sometimes a powerful plot device and Merlin has occasionally found himself performing a feat of thaumaturgy that most of his peers would find impossible, usually after sending the benefactors on some long and arduous quest to find some critical McGuffin that is missing as an ingredient for the spell.