Humans have wings too. Some of them anyway.
Incorporeal, they’re like the vestigial organs of the soul. Even harder to see than souls- usually only even vaguely visible when someone is being born or dying.
So obviously the Winchesters had to break the rule. Their wings were visible to any angel. Gabriel was sure that Castiel stared at Dean’s face so fixedly so that he wouldn’t end up staring at his wings (beautiful, powerful condor’s wings; almost pure white.)
Sam’s are dark blue hawk’s wings, almost black in places; wings of the messenger. Gabriel resists the urge to touch them. It’s easy, he tells himself. He has the entire world as his playground. Biggest chocolate fountain in the world? In his kitchen. Biggest swimming pool, with fountains and a miniature waterfall? In his backyard. Have a day off to see the planet made of diamonds. Or go off and play connect the dots in the Medusa Cascade.
It isn’t easy, even when he’s miserable and hates Sam and hates himself it isn’t easy.
Then there’s the day he almost dies and Sam’s wings curl around him protectively (Gabriel remembers these are the wings of guardianship) and honestly, man, there’s a limit to which you can push an archangel yeah? Gabriel runs the back of two knuckles gently over them and they surround him completely for a moment before jerking back in a hurry.
Gabriel is somewhat surprised and somewhat amused to see Sam looking intrigued. He grins up at Sam and looks forward to the treat he’s going to get.