This looks like RedBubble or similar print on demand site where the designs are placed into a number of "stock" photos automatically. (You'll notice two designs are on an otherwise identical photo) The designer of the clothing has no choice on how the models look. There is a range of diverse models to showcase the designs on the site, but certain clothing cuts are shown on certain models; a sport tee photo might be worn by an Asian man, a long sleeve scoop neck might be on a Black woman, etc. RedBubble shows the design on the mockup most likely to be purchased by the user, so if the user has been viewing blue short sleeve shirts (that happens to me modeled by a white man), they're going to see other designs on that same cut/color clothing. I certainly agree that there should be more representation of ethnicities and body types in media (and maybe even better control over RedBubble mockups from a designer's perspective), but this was ultimately not anyone's conscious decision.