The one thing alot of people don't understand is that in the box stores, when they bring a shipment of birds into the general population if one of those birds is sick, they have just infected "what may have been healthy birds". Not only that if you already have birds at home you can pick up whatever they are shedding and take that home to your birds. In the event your birds get sick you may not have thought to tell the vet that you visited one of these petstores.
There has been one store in particular in the papers over the past couple of years that had to pull all of their birds due to some nasty illnesses.
I do volunteer at an avian rescue in my hometown. Any birds they take in have to be quarantined for at least 30 days and vet checked before they come into the program. People interested in adopting, which is a good thing, are required to take two classes and spend time with the birds and interact with them.
Unfortunately when you go into the box stores and general pet stores their goal is too make money
they don't have the knowledge to pass on to a new bird owner that the bird could outlive them,they need vet visits and that they may not like all people in the family. Nothing irritates me more than a person going in for the status symbol and when that wears off, these birds are forgotten about or become pluckers or screamers.
If someone is interested in having a parrot, google avian rescues in your hometown and check them out. I will agree you could run into a bad one. See how the birds are kept, check out their food,pellets,fresh veggies and fruit the substrate in the cage should be paper not would shavings or cat litter or corn cob, this stuff can create a new beast to deal with.
If it feels bad you'll know it. I'll get off my soapbox now.