If someone sits at home and very rarely flies makes DM through AMEX MQMs the only advantages I can think of for this person are: (i) the ability to redeposit SM at no charge <T-72; (ii) getting through quicker on the phone; and maybe (iii) getting the benefit of the doubt in the resolution of a subjective grey area/rule because of his loyalty (i.e. a schedule change of <90 minutes). None of this should affect any other DM traveler’s life including their ability to get an upgrade.