If you actually have both a PS4 and Xbox One, wouldn't you want to know which version runs at a higher resolution? Some people will simply buy the version where their friends are, but others like to buy the version that looks the best.
Regardless of whether you think it doesn't matter to you personally, or whether you cannot tell the difference personally, it does matter to some people who simply buy the version that is confirmed to run best. Its that simple! It's not a case of whether you have to have both version side by side to tell a difference, many consumers like to educate themselves on items they want to purchase, and knowing the resolution a game runs at is important for many people, especially if one version of a game is going to run at a higher resolution than a different version.
I know this may seem kinda difficult for you to understand, but for people that have a choice between buying on one console or another, they like to get the "most bang for their buck." If you only have one console, it may not affect you at all since you cannot buy the other version anyways.