I think it’s a combination of things. Costner did shoot a nude scene for the movie For Love Of The Game but it was edited out when the audience in a test screening spent more time talking about Costner’s cock then the actual film. He also had a nude swimming scene in Waterworld which was also subsequently cut from the final print. I think most of these instances were due to the studios and/or producers deciding not to put a penis on film less the film receive a more adult rating rather than offending audiences. I believe some (many?) in the audience would be more than okay seeing Costner do a full frontal scene today, especially given Kevin’s size, if it were tastefully done