Correct me if I'm wrong. The issue with SNPs is that they are common in the population, and hence they tend to have small effects, because if a variant is commo

Correct me if I'm wrong. The issue with SNPs is that they are common in the population, and hence they tend to have small effects, because if a variant is common and gives the carrier a big advantage, the variant will over time get absorbed by most of the population, and the same applies the opposite way. So the interesting variants are those that rare, because they are the ones that often cause genes to malfunction.