The genetic trait was desirable, but to control the population a "limiter" was set in place.
In FF16, this limiter is the "curse" that turns bearers into stone if they channel too much aether.

We see this in the "interdimensional rift" when, where Ultima says he punishes the unruly. It raises a lot of questions.

In FF8, Diabolo's scan data says it's a GF from another dimension. ~What does it mean~