American marketers, like all other employees, must do their work in a way that will please their intended audience. Which unfortunately aren't the end customers. The marketers' real audience is their own company's executives, and the presentation of their work is their ultimate opportunity to be recognized.
Because they have 1 opportunity per product, it's a formal presentation, and all the people watching are really important to the marketers' careers, they will always choose something that has a clear message and an immediate visual impact. It's not like the executives actually understand what the game is about - the just have a brief to go on and are there to rubberstamp whatever looks like it will sell.
And it's easy to hold up a competitor's product with flashy colors, Chuck Rockjaw kicking @ss in the foreground, and half-dressed women in the background next to your spare, deeply meaningful, artistically pure evocation of the game's true character and make the subjective evaluation that your sales numbers didn't meet expectations because "their cover just looks better". No American marketer is going to risk career suicide in order to create art when they can put out something that looks good on the shelf and adds job security.
