Well, he is a princess of some sort, he's got interdimensional connections with royalty and not royalty (Roy, for example), some monsters (through Star though), Heckapoo, he's also almost a celebrity, he has (or had) his own nemesis (Meteora), he is a "bro" with Tom, he helped to save the kingdom (sure, he wasn't the best savior, but hey, he is a 15 teen and tried to work with what he had and knew) AND he has his own scissors.
Funny thing, Marco doesn't actually need Star if we don't speak of his feelings for her.
Moreover, technically, his position, wealth etc. he should be in the same position for Butterflys royalty as, I don't know, Rich Pigeon, who is basically a pigeon with legs, however "he is rich".
And technically half of the knights and all squires should've pee their pants before they even think about laughing at him. Even Heckapoo finds him worthy enough to fucking betray her job and MHC only for his "adult voice", moreover she's kinda jelaous and sad of him being Star's squire when he could literally be an interdimensional hero.
It's funny, how having so much potential and possibilities Marco throws himself that low. And that's not because "muh Star" actually, he could've gone "muh Star" while staying awesome.
But he is still not ready for all the good shit he has. Kinda like Star wasn't ready for her wand so she had to go to Earth and take some time. Now it's the other way around.