It was invented around 150 years ago. During the early age of steam, when engines were much less efficient than today and re-coaling/re-fueling infrastructure

It was invented around 150 years ago. During the early age of steam, when engines were much less efficient than today and re-coaling/re-fueling infrastructure much less widespread, sail + engine arrangements were common. My understanding is that cargo ships usually operate on rather thin margins except during a occasional fat times (like right now)... If new sail designs were actually economically beneficial, ship owners would adopt them ASAP. As the quip goes, they like money. Color me cynical, but I don't really think they care too much about the environment.