They are fairly different applications, but yes sailboat rigging lines are subject to significantly greater loads, greater cycles, more abrasion, and more UV light. Sunlight and salt water along with static high loads and significantly more cycles of loading result in higher standards. Winch ropes are usually SK75 or some lesser version. They are basically the cheapest level of UHMW rope. It's a lower grade than what's usually considered the bottom grade rigging line for sailboats.Salt water harder on rope than mud, sand, and dip spit?
And boats are also a lot bigger. A 20k lb sailboat is not really even considered "big". A 20k lb off road vehicle is - well - I guess that's a typical overlander Tacoma? The main point being that even mid size boats have loads on the rigs that would break any typical consumer winch rope.