They try. For example Instacart shows you "recommended" items at multiple places in the shopping flow. However I think there is some sort of limit here because it feels more explicit. If I search for something it is obvious when you are putting results that don't match in my way. In the store it is easy not to realize that the things that you want are intentionally spread out.

Mostly, limited visual field. Screens aren't able to lure you in through peripheral vision