Because plantains are cooler than bananas.

Way, way cooler. Plantains are so badass, they can’t be eaten raw. You can just pick a banana off the street and show that plucky yellow fruit who’s boss. It’ll be wasting away in the gastric confines of your stomach quicker than you can say, “plantains rock!”
Yeah, just try that to a plantain. Nope. You wanna take on one of these suckers, you had better bring some fire. Plantain: man’s natural enemy. It also turns yellow or black when ripe. Black! The color of coolness. Don’t mess with the plantain.
Do not mess with the plantain.
Well. Hello everyone.