Reasons For Service Dogs

Nowadays, service dogs are a common sight in the society. Basically, they are canine companions strapped with a vest accompanying people with various disabilities. Though it's tempting to pet one, here are the reasons why you should never do so.
People get service dogs for a number of reasons, but this is usually because of an illness or a disability. Some are trained to guide blind people and give them signals. Others meanwhile, can even detect seizures (though it is unclear as to how), and react to certain situations, like what to do when an owner is having one.
When you pet or distract a service dog, you're actually endangering the life of the owner. If you approach and pet a service dog, its attention deviates from its owner to yourself. This in turn may make it NOT detect an incoming seizure and be less aware of its surroundings.
Photo from K9Alliance.

Some people actually feel sorry for service dogs. The reasons behind these feelings are "they can't enjoy life" or "they're not well taken care of".
However, please note that these sentiments are unfounded: service dogs are happy dogs. They are valuable, well-taken care of, and are great friends to their owners.
Basically, there are two "modes" in being a service dog: work and normal. The work mode is activated if the owner puts the vest and leash on. By doing so, the dog knows that it's time to guide or help its