Think about these questions.
Can you afford to throw the money from your holiday away should you not go for <insert reason> ? ie medical, work, death in the family, disney closes, airline goes bust etc etc
Can you afford to buy another flight should something happen? ie airline goes bust, you need to get back early, or you miss your flight
Can you afford to replace your luggage should it go missing?
Will your healthcare cover you?
Can you afford to replace valuables that have been lost/stolen on your holiday?
Insurance is worth it in the even something happens. You pay house and car insurance every year and nothing happens. Holiday's are the same. You may never use the insurance but should something happen you will wish you had it.