Why should I pay for and get shingles vaccine if it only occurs once if at all?

Shingles isn't fun. Ask a few people about shingles and they'll tell you it can range from annoying to really painful with symptoms that last months after the rash is gone (postherptic neuralgia). There's no great predictor if you'll get a mild or severe case. And yes, you can have it more than once in a lifetime - i've seen people on their 2nd or 3rd episode. The cost isn't trivial, but shingles isn't either.
Waning immunity. The shingles shot boosts the aging immune system. Get it & decrease possibly of getting shingles & your risk of spreading the germ from the weeping sores. The location & extent of the outbreak is variable. You can chose not to be vaccinated & take your chances as many do yearly with the flu shot or you can take advantage of the technology to avoid an problem. The choice is yours.
Prevention. Vaccination reduces the incidence & severity of herpes zoster, as well as the incidence of post herpetic neuralgia, a painful condition affecting your nerve fibers and skin. The burning pain associated with postherpetic neuralgia can be severe enough to interfere with sleep & appetite. The risk of postherpetic neuralgia increases with age, primarily affecting people over the age of 60.