Oh, poor Ms. Marvel!
The face of feminism (Ms. in 1977!), Air Force Major Carol Danvers was hybrided with alien DNA and took the she-name of her boyfriend, Captain Marvel.
Later raped and impregnated, then her powers and memory "permanently" absorbed by the X-Men's Rogue (pro—made Rogue pretty awesome; con—everyone wanted Ms. Marvel back anyway). Along the way, powers and name changes from Binary to Warbird back to Ms. Marvel and eventually emerging as the most powerful woman in the Marvel U., she changed her name to Captain Marvel.
Captain of what? Whatever her ex-BF was captain of (the Kree intergalactic army?), she isn't. But it's in honor of all that he meant? Weak.
Ms. Perfect or Ms. Plays Her Music Too Loud would be titles of a kind meant to amplify the quality the bestower intends call out (usually for negative reasons). If there was a heroine "Ms. DC," one would assume she is the embodiment of the DC universe or the line of comics. So, Ms. Marvel (regardless of her ex BF) name suggests she's also the embodiment or flagship heroine of the Marvel universe. Certainly, that's how she seems to be positioned lately.
So, why would a determined and strong woman, who had earned the rank of major, and held the name that embodied the comics line she represented, take a lower rank on all levels, of captain? To me, she'll always be Ms. Marvel, midriff exposed with a giant scarf.