That doesn't match my experience. When I have a large reserve of frequent flyer miles I am generally treated quite well, actually. Frequently I have been bumped to first class gratis, or "economy plus" if that is what is available, given discounts/rebates on luggage and other fees, offered complementary access to the airline's lounge/club at the airport, etc. This is all above and in addition to the usual perks, like priority/VIP boarding order or whatever.
"Frequent flier miles" don't mean a thing on any major US airlines. The only factor in how they treat you is your overall profitability, which is calculated in elite qualifying miles (EQMs). This is what determines your status and your status determines your perks. These miles come from buying high cost-per-mile tickets, i.e. a $300 SFO-LAX fare, a $20K international first class R/T from IAH to LHR, etc.
