Some paddlers use inflatable pfds for a bit of reassurance but minimal interference with their stroke. And some warm water cultures (Hawaii for example) may largely ignore the use of PFDs, but the statistics on drownings in cold water climates should make the advisability of wearing a PFD on cold water in most circumstances clear (there is a case to be made for exceptions such as racing in otherwise benign conditions with organized safety support).
Baltic Argus inflatable PFD Demo/Instructions