The problem here is that you're assuming a) psychic abilities would have some degree of heritability, instead of being random accidents that aren't passed on genetically, and b) that psychic abilities can vary in degree, so that there could be selection pressure to make them larger, instead of being binary.

Also consider that psychic abilities in small amounts could have detrimental effects on fitness: for instance, they could make you more sensitive to bad moods, more temperamental, or even insane.