One of the things about superhero costumes is that they originally had the premise that heroes wore them under their clothes, so they could change quickly when needed. I believe Superman supposedly also had a hidden pocket in his cape to hold his Clark Kent clothes.
Now, they don't bother with any of that, because they want textures and layers, which would be impossible to hide under normal clothes (though I'm not sure how realistic it was to hide a costume under regular clothes). Every costume just appears from "nanites" or some such relatively nonsensical explanation. That's one of the things I disliked about the progression of the MCU. Iron Man started out needing an apparatus to get into armor. He had the suitcase armor in the 2nd film, but it still had more of a "real world" feel. Now, they just appear by magic tech.