Let's think about this for a moment. Kingmo is qualified as a Foster pet provider but wouldn't qualify for adoption. This is confusing Quincy, maybe it's the chicken vs egg controversy.
I think that the problem is a bit different than you might think. 1) As previously mentioned here there are people who dog flip. They might agree to foster a litter of puppies or kittens that are enough of a pure breed that they could sell for a decent amount of money. They might adopt just to be able to sell the puppies to the highest bidder.
Or, someone might qualify to foster for the short term, but have too many other pets to be able to adopt. There could also be other reasons that I have not though of.
However, in the end, I agree with Quincy. It is better for the animal to be with someone with whom they have already bonded.