“a good wing does not require winglets”.
Probably true... I'm not an aerodynamiscist.. Supposedly the winglet will reduce induced drag..it also acts as a wing fence and generally improves performance and fuel efficiency...
There's usually more than one way to do a job and using a winglet as opposed to developing a more efficient wing is an option...
Interesting that one of the most aerodynamically efficient (and maybe THE most aerodynamically efficient aircraft outside of the military), the Piaggio Avanti, does not have winglets.... a result of something over 70 hours of wind-tunnel testing... the average military fast jet would typically get about 40+ hours of wind tunnel development.