Being given conflicting information about vaccinations can be confusing and frustrating. There always has been and likely always will be differing opinions on vaccinations among not only local veterinarians, but also by experts in the field of vaccine science. The purpose of vaccinations is to prevent disease not only in individual pets but in populations of pets. The same philosophy applies to vaccination recommendations and requirements for children attending school.
Vaccine recommendations take many factors into consideration including the prevalence of disease in any geographic area, the risk of exposure, the likelihood of becoming ill if exposed and the likelihood of dying if infected. As an example, consider the rabies vaccination, which is required for all pets, regardless of lifestyle (indoor versus outdoor only) and prevalence in any particular area. Because rabies is found in wild animal populations, every pet has the potential for exposure because ill animals act in uncharacteristic ways (raccoons wandering around in the middle of the day, bats flying inside houses). The likelihood of becoming ill if exposed is somewhat unknown in many circumstances, but the risk of dying if infected is 100% in pets and also in people who don't have post-exposure treatment.
Vaccinations are often divided into "core" and "non-core" groups. Core vaccinations include (but not only include) distemper/parvo vaccinations for dogs, distemper vaccinations for cats and rabies for both dogs and cats. Non-core vaccines are those that may or may not be recommended for all pets. If you have a dog that spends time outside in places where they are constantly exposed to ticks, vaccinating against Lyme disease may be recommended. If you have a house dog that never goes outside, lives in the middle of a big city in a state where ticks aren't an issue, vaccinating against Lyme disease may not be considered appropriate. As a pet owner, you can listen to your veterinarian's recommendations for vaccinations and understand the reasons behind those recommendations. Ask questions and get clarification for anything that you need additional information on.