Maybe they don't care enough about that extra stripe to take the pay cut or to work more.

As for the "never intend to command" phraseology, some absolutely did "intend to command" but once they got to senior FO they realized their pay was very good and QOL was amazing and they didn't want to give that up. Likewise I know some who chase the left seat even for a pay cut and a worse schedule because they "have to be Captain". Now that's something I never understood.