Well, if the wind is at your back, I think it’d just be more efficient to use sails, since it skips conversion losses. If it’s a headwind, well you’re just adding drag. You can’t put wind turbines on a vehicle and come out ahead of sails.
Sticking a wind turbine on your boat, on the other hand, is basically regenerative braking. You turn the excess speed you don’t want/need at the time, into stored power for later when you do need it, to exactly the degree to leave you with the speed you want. A tailwind is to a boat as “going downhill” is to a car.