Petco is a business. They want to supply products and animals that customers will buy. You, as the customer, can help mold how Petco operates as business. When a person "rescues" cheap, imported normals, they are ironically telling Petco that they want them to carry mite ridden, sickly ball pythons. When a person buys a healthy, well taken care of morph, they are telling Petco they want them to carry snakes that are healthy and bought from a breeder (hey maybe even one day it'll be from a small one that's local to the store). Petco is only responding to the people who buy their animals and taking their husbandry and stock cues from them. It's simple supply and demand.
I don't think you need to justify your potential purchase to anyone but, if you need justification, people do help shape Petco's husbandry and stock decisions with purchases like these.