Your veterinarian knows you and knows your animal(s), and this is critical to keeping your animal(s) healthy. For example, your veterinarian can customize a vaccination program to give your animal the best protection from disease and make sure that it isn't getting a vaccine it doesn't need. Vaccine and drug reactions, although uncommon, can occur, and your veterinarian is trained to recognize and treat them to minimize the chance that the reaction will become severe or even life-threatening – you can't get that from a website!
Figuring out what's wrong with an animal is like solving a very complex puzzle – your veterinarian has to figure out how to fit all of the clues (pieces of the puzzle) together to solve it. Veterinarians have, on average, 8 or more years of college and in-depth veterinary school training to prepare them for this task. Their training makes it possible for them to thoroughly evaluate, diagnose and treat your animal's problem. Doing these things effectively involves thorough knowledge of your animal's body systems and how they function, as well as a familiarity with how medications and other treatments work and if any treatments interfere with others. Hands-on physical examination is incredibly valuable to your pet and can't be replaced by a phone conversation, web-based conversation, or email description.