Answer;
This is because the genotype may be have recessive effects or dominant effects.
For example; Genotype RR AND Rr are going to produce the same phenotype and look the same, but the one with the Rr has recessive gene.
Examples;
-Genotype is the organisms genetic makeup or allele combinations.
-Phenotype is the physical appearance or visible traits.
A dominant allele is masks the effect of recessive allele making them not visible or seen phenotypically.