Granted there may be some down sides to 26" wheels on the back of trikes, but the fact remains a 26" wheel gets the chain and RD much further up out of the dirt and trash. Then there is the fact that with a 26" rear wheel, you can use available mountain bike gearing.
Also there is no logical reason for it, but a trike with the 26" rear wheel just looks better.
Last edited by rydabent; 02-15-20 at 07:26 AM.