Depending upon the character creation rules you might have a scenario where instead of making a ranger the optimal choice becomes customizing your fighter to make him more ranger like same thing with your paladin or rogue. If the fighter is superior to the other melee classes how do you protect those classes without making the fighter the guy who can only do athlectics endurance intimidate etc?
Yes, that's a good reason not to simply make the Fighter the best at fighting. There will be an intense pressure to just play a Fighter, and get as much non-combat stuff out of Backgrounds as possible, to get both the best fighting, and "good enough" non-combat. Since when dealing with DM fiat, all a player really needs is something to point to when convincing the DM to let them do something.
My ideal would be to balance all classes on both combat capabilities, and non-combat capabilities, and only have serious tradeoffs within those two spheres. But that doesn't seem like what they are going for.
However, if they do have some awesome non-combat mechanics in store for us, than I'd be more OK with having the tradeoffs between combat and non-combat they seem to be going for.