Perhaps a related question is why does no one eat barley?
It's GI is lower than oats considerably (for pearled or hulled), it contains more fibre, both souble and insouble, and comes without fat. This could be seen as a bonus, because oat fat contains a fair bit of omega 6, so if u wanted the fat, u can add flaxseeds or almonds etc.
Is there any reason why barley is not > oats ?