Essentially HBO (Basic) revenue fares came about fairly recently, because of fare comparison websites including low cost carriers. Because LCC baseline fares don't include checked luggage, BA was always going to look massively more expensive, particularly from LGW, whereas if you were to add baggage costs to easyJet's fares then BA would look fairly competitive. Since the websites and easyJet have a vested interested in not doing that, the way around this was to create a Basic fare structure which allows a head to head comparison. This was initially done for European sectors, then when Wow! (RIP), Monarch (RIP), Primera IRIP), Norwegian (still with us) started LCC flights to longhaul locations, the same principle carried over.

Since LCCs don't have frequent flyer schemes on the whole (Norwegian does have a cashback scheme, and easyJet is about to widen their frequent flyer benefits) then there is no need to compete so fiercely with Avios bookings.

It should be pointed out that Main Cabin redemptions on AA are HBO, in line with all their baseline fares.