Hi Cider:
Would I be right in guessing that you've never had to claim? The reason I ask is that you surely would realise that had you made a claim when your insurance is protected, you would find out come renewal time that your premium would be increased fairly significantly.
The so called benefits of protected insurance is that you're allowed to make a certain amount of claims within a specified period without your no claim bonus being affected.
The downside, however, is as I've already mentioned that should you do so, you'll certainly "pay" come renewal time. The insurance companies don't normally labour this point, they just trumpet the "no loss of no claims bonus" part.
It's a swings and roundabouts situation, i.e. "just in case", like any type of insurance. A necessary "evil"?