What's the point of giving the main character a special power that they never use?

In many anime the main character has a special power which gives them an edge over others but they never use it. We can see from their past that it was a special power but now everyone can have that power. In my opinion if the anime is going to make everyone be able to have that power they shouldn't give it to the main character. This might not be the case with many anime but it is true for some.