1) they don't want to take more of a loss than they have to go get you in the door, 2) the people who buy diet coke or diet Dr pepper are statistically more likely to shop sales than the people who buy non-diet, 3) the relative allotted shelf space and display area aren't just a store manager decision, but actually a product the grocery store sells to the manufacturers, 4) (2) & (3) imply that stores in different class areas of town might have very different which product sells quickly and utterly fail to optimize stocking of the thing you noticed when it literally never sells out at the Kroger a mile away, for example.
Just look at the pricing between different serving sizes. Their price differs often less than 30%, even if you compare 0.5l to 2l.
Me, I like cans. They’re about 35¢ apiece. That’s cheap enough to not worry about, and way better than getting a fountain soda at a fast food restaurant.
Market segmentation at its finest!
My ideal is soda fountain machines, but of course I'm not gonna have one of those in my apartment, so the next best is cans.
Every time, without fail, the Diet Coke column is nearly empty while the Coke, Sprite, and Coke Zero ones are full. Not only that, but Diet Coke gets the smallest portion of the endcap.
My only rationale for this is that these are loss leaders, and the Diet Coke is too popular to allow too much room? I don’t know.