I think the reason people might be looking at Mileage Multiplier ir because Amex "incidental" credits on Gold/Plat/HH Aspire/etc stopped working with AA gift cards earlier this year, and Mileage Multiplier,as poor a value as it is, is one of the few AA things available to "all" that now work reliably for that $100/$200/$250/whatever credit from Amex if AA is your selected airline. (Baggage works but if you have status or just always fly carry-on only that doesn't help. Seat selection might work but if you have status or don't otherwise pay for seat selection, that doesn't work.)