For snorkeling I don’t think there’s a need for it. However, the camera itself is only waterproof down to 15 metres which is quite a shallow restriction for diving. My ikelite housing is rated down to 60 metres (although I’ve found anything past 40 metres and the buttons stick so much it becomes unusable). Most divers will be going to a max depth of 30 metres so the housing will allow them to take the camera on most recreational dives.
Since I’m using it at depth, I never submerge mine without the housing. It’s just extra protection against the damage of saltwater. But I know it’s designed to withstand that and a proper freshwater rinse should be sufficient to maximize the lifespan.