It probably depends on the pet store. In my experience, privately owned "mom and pop" places are more apt to be carrying wild caught snakes - things like garters (native and indonesian) and other common colubrids. In larger national chain stores, you're going to see mostly ball pythons, corn snake morphs, and on occasion something like a kenyan sand boa, milk snake, or king snake - and they'll pretty much always be captive bred.
Though personally, I'd skip pet stores altogether: you're paying twice the price for an animal that isn't nearly as healthy as one from a reputable breeder because most stores have their husbandry 110% wrong, and even if they don't, they are sourcing their animals from the wild or from mass breeders that tend to throw poor quality stock since the emphasis is quantity not quality. Thankfully, healthy captive bred snakes are available all over the place from private hobby breeders - check out sites like kingsnake.com for listings, or simply attend a local reptile show for a wide selection of reasonably priced herps.
