More:
I've seen some places use the high shelves for storage - the "extras" are kept up there and brought down as needed.
I think many/some people have afflictions that make it difficult for them to reach and push - bad shoulders, arthritis, old age, etc.
so maybe a sign or something that says something like "We love to help - let us know if we can make something easier for you to see" - if you have the staff available to do so.