Because it is funny, on the surface.
But, when you think about it, GOTG can just be viewed as another film with a white male lead, not some talking raccoon.
From what I've read, it has to do with foreign BO. So, studios are less willing to spend the type of money they do with big budget films that have white male leads than those with a female and/or minority lead. Thus, it's "hard" to make films for character like WW or Black Panther from the get-go an their best bet is spinning off some other film or being low budget (which would probably hurt the film).