In nature, mutation rates aren't usually high enough to maintain alleles that are not favored in a population by natural selection.
While in the wild, many populations are led by natural selection. This means that favorable traits are passed down through generations, while unfavorable traits are not. Traits that are best suited for the environment of the organism will prevail to help the chance of survival.
Mutation rates usually aren't high enough to create traits that are unfavorable to an organism. While mutations are still possible, it is still unlikely. The traits that are chosen by natural selection are most likely to be passed onto organisms and their offspring.
