Rob,
In my opinion treatment risk is essential, if only for peace of mind. However, if doing mainly domestic work, it does sometimes make you wonder. Most if not all nsurance companies settle claims on an indemnity basis, i.e. on the value of the item at the time of damage and not on a new for old basis. With a usual £500 excess imposed on most policies, that amount or less would probably cover the reninstatement value wise of most used carpet or upholstery, BUT if they are only a year or two old, might not! Tempting though it may be to drop the cover, I think I think I'll stick with it.
Dave.