I guess this is just part of their business model: to do what they can get away with doing. Very few people - myself included - are prepared to spend a lot of time arguing with AFKL CS over just a few miles. Interestingly my new carrier has no issue crediting miles for inflight purchases. They may not buy me a lot, but it tells me they have their act together and value my business enough not to nickel-and-dime me over small stuff.