Yeah the blood hting is stupid, but that is a comic book thing. In comics, and I guess shows based on them, the characters almost never change their look, so they can't change their clothes. If they got blood all over them, they would have to explain why they changed into another copy of the same clothes, or have them change into different clothes which they almost never do.
You even see them doing laundry which is hilarious since they have been wearing almost the same thing for months now
