I remember reading in a Red Sonja comic that the character wears a skimpy top and bottom to distract her mostly male adversaries. WW's costume isn't quite as trimmed down, but could be explained as a similar tactic.
I'm with E in general though, the comic costumes just don't translate well to the big screen. Hawkeye is one of my favoite Marvel characters. Initially, I was really bothered that they weren't going to use the purple and pointed mask in the movie, but after seeing how Cap looks, I realize it just wouldn't work right. Styles and protective gear have changed since these characters were created, so it only makes sense to modernize them, just like they modernize the stories (e.g. Iron Man as a captive in the Vietnam war vs. Afghanistan).
Here's a surprising twist though: I was reading my latest Avengers comic and noticed a new costume for Hawkeye. He just showed up with it, so not sure if I missed a story around why he changed, but it is MUCH more similar to the film look vs. his old costume. I wonder if we will start to see more of this trend, where the comic initially set up the movie, now it looks like the movie will drive some of the appearances we see in the comics. It makes sense I guess for branding, but seeing stuff like that always makes me feel like someone sold out.