Purpose of VaryByRouteValueNames

Hi, I’m a bit confused about the purpose of VaryByRouteValueNames. The effect seems to be that it adds to the cache key a value whose name and value are taken from the route. However, at the moment the cache key already includes the entire path, including any values from which the variable parts are extracted.

Is there a use case where it’s suggested/required/mandatory to specify VaryByRouteValueNames, if the entire path is already part of the cache key?

Thanks.