Although surviving an ocean ditching may be statistically low nowadays, the rafts, life jackets, etc are a bit of a throwback to when a survivable ocean ditching was quite possible.
Aa ocean ditching many miles from land is not the only relevant scenario. We have had examples in recent years of landings in rivers at relatively low speeds, and runways with water at one or both ends are not unknown. Lifejackets and rafts may be very valuable in case of accidents in such locations.