the only villain on staff
Which is why the title is useless. Sora has accomplished plenty with the power of his friends. He did the exam for Riku's sake and not his own. Him not passing, regardless of the reason why, meant nothing to him and it is supposed to mean nothing to the audience as well....Especially when in all intents and purposes, he should have the title. He's accomplished far more than any actual Keyblade Master we've seen has, I mean.
The title only carries weight in the eyes of those who are willing to recognize it. Riku felt like he was still worthless and filled with self-doubt, and so the title gave him a sense of purpose.
Terra put so much importance in the title that he was blindly sought out power due to his perceived failure.
Aqua didn't want the title and spent the entirety of BBS ignoring it, but had to accept it as it was her responsibility.
Sora didn't want it, didn't need it, and didn't get it so he has no use for it. This also makes Sora an exception to the rule because he has ignored all traditional routes that other Keyblade wielders had to follow to gain power.
Essentially, the existence of the titles and inheritances and whatnot is supposed to show how the traditions surrounding the Keyblade are intrinsically broken. They were put in the series to be a broken mess. We are supposed to not like it and it is supposed to not be useful or beneficial to the characters.