I wouldnt say ADA is, it's everyone being scared of enforcing it or running afoul of it. For example. Cat's are not valid service animals. Currently only dogs and miniature horses are listed under ADA.
But by ADA laws only 2 questions you can really ask people. "Is this a service animal required because of a disability" and "What task is the animal trained to perform." Unfortunately there are no guidelines on what acceptable answers are. Good fakers just say it's a seizure dog. The usual idiots never encounter the 2nd question and freeze up before answering therapy animal or some such.
Under ADA there is no simple "comfort" animal aka an animal that it's mere presence is therapeutic. However gray area as what is recognized is an animal "trained to calm or distract the handler" during like a panic attack or bi-polar sperging out.