That's not true. I know a dog trainer who trains real support animals for the veterans, the handicapped, the blind and even drug sniffing dogs for the police. It a long laborious process. Then there is a two month process of training the dog's new owner how to handle it. I'm not saying every animal that people try to pass off as a support animal is an actual support animal trained like this but some certainly are.
Those are a drop in the bucket, and are basically the same as “service animals” for the disabled.
Most of the ones out there nowadays are just regular pets with a vest someone bought off the internet slapped on them.