There are varying degrees of effectiveness with most any tool you might use to maintain your edges, depending on the existing condition of the edge when you're trying to tune it up. You might find that you can maintain your edge with a strop most of the time. But there'll be occasions when the strop may fall just short of putting enough bite back into an edge. With extended use and many touch-ups, strops tend to eventually polish a lot of the 'bite' out of an edge. At times like that, you might find the rod to be perfect for that 'little bit more' needed to get it done in the moment. You might also find that the character of the edge, coming off the rod, might be preferable to what you get from a strop, at times.
Point being, the strop isn't always an ideal substitute for the rod, and the rod may not always be the ideal substitute for the strop. Each has it's own uses.