Probably the principkle advantage of a fresh water boat is that, in most areas, it is in the water for less than six months per year. If you are in a northern clime and lose the ability/desire to sail, you haul your boat out and store it, as leaving it afloat is not an option. If you are in the same situation in salt water, it is possible to leave the boat in the water, and the degradation of components continues apace. The humidity and alkalinity of a salt water environment play havoc with many parts of the boat, seen and unseen.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.