The answer to the question is that Goodell and the NFL are cowards.
This stunt by Kaepernick may well be the tipping point, though.
Charlie Goodell them immediately stopped on a dime ideologically and made a 180 degree turn to the hard left as a Senator. Spiro Agnew, with Nixon's blessing, went to New York State, labeled Charlie Goodell as "the Christine Jorgensen (a briefly infamous "transgender" who had eagerly submitted to chopadickoffame surgery in Scandanavia) of the Republican Party, endorsed Conservative Party Senate nominee James Lane Buckley (Bill's elder brother) and totally upset NY politics in the process.
Charlie's boy Roger is a quisling just like his daddy. Conservatives should have walked away from the NFL unless and until Goodell was replaced by a principled American. For a decade or two, I have comfortably avoided any perceived compulsion to waste time on the NFL.