True service dogs don't even start the specialized training until they're 2+ years old. The first two years are socialization, becoming comfortable and unfamiliar settings, getting used to things that they might not otherwise get used to (medical equipment, elevators, buses, etc). Then after that there's intense training and whatever feels that specializing in. And if their training requires detecting some physical conditions by scent, the average person often doesn't have access to that scent in a controlled manner which is required to properly train them