mcdonalds has never offered onion rings on it's menu to my recollection, why not for competition purposes ?

They sell onion rings in some overseas markets, the UK for example. They've been test marketed in the United States, but they never sold well enough to make it as a permanent menu item. McDonalds primary market is families with young children. The kids see Ronald McDonald on every other commercial, and they want to go get a happy meal with this weeks toy. The kids don't like onion rings. The parents go along because it keeps the kids happy and busy, they can play in the playground or whatever. They don't really care what the food is, so long as it's cheap and their kids will eat it.

Probably because no matter what most of the foodie people think of Mcd, the fries usually get a very high rating. Screwing around with onion rings either compromises the grease and screws up the fries or brings in a whole extra process; pretty expensive.

Sometimes you quit while you are ahead; or don't fix what ain't broken.

Because it's their fries that's world famous