[BoredGuy]

I'm not saying the mask would be easy to make look good, but it could be done.

Hawkeye, I think with his limited screen time, his revised SHIELD origins, and the oscar nominated actor playing him, these things resulted in no mask for him

And don't even get me started on Catwoman in TDKR
You don't need some real-world plausible reason, it's their iconic look
There was no reason for Michelle Pfeiffer's catwoman to have the cowl, but they made it look great.
Anne Hathaway's Catwoman outfit was a lame attempt from people who were uneasy embracing the comic book their comic movie came from.