Pet store puppies are almost always very ill and tend to need several (very expensive) trips to the vet. There are dozens of complaints online about sick puppies coming from major pet store chains.
It's also easier, because if someone has the money, they get a puppy: No questions asked. Does the pet store employee really care about the puppies welfare by letting it go to any Joe Schmoe who has a credit card?
The pound will ask questions: "Do you own your home? Have a fenced yard? Have a Veterinarian in case of an emergency?" Yes, it's more of a hassel. but the 'pound' wants to make sure that puppy will not end up there again in 2-3 months, like many pet store dogs do. People working in shelters aren't there for the paycheck, like many pet store employees are. They're there because they have a passion for helping animals. Most of them work on the clock and off, rescuing abused, abandoned and less fortunate animals and giving it everything they have to make their lives better.
Also, when you adopt from a shelter, the price is normally 1/10 of what you'll pay at a pet store and the dogs/puppies are already neutered, vaccinated, microchipped and have had full physicals. Pet store puppies will come to with their first puppy vaccine and 1 dose of dewormer.
Lastly, a pet store puppy is usually an impulse decision. You're out shopping on a Saturday afternoon, you just happen to go into the pet store and get hooked in by those precious little faces. You're willing to pay any price (usually $800+) to take that little fluff ball home with you before someone else does.
But...with that adorable face comes pooping on your carpet, chewing your favorite pair of shoes, eating the remote, whining to go outside to potty (if you're lucky) at 3 a.m....The novelty wears off very quickly and suddenly that once adorable puppy isn't so cute anymore and through no fault of his own, will end up at the shelter.
People who adopt from shelters typically have already given it some thought and planning. You normally don't end up at the pound on impulse, like the pet store. People are there for the specific reason to adopt. They pretty much know what they're about to get into and ready for the commitment and will more than likely keep that pet for it's lifetime.
So is it easier to buy a puppy from a pet store? Yes. Is it better? Absolutely not. "Adoption Is The Best Option"