Actually, the meaning of 1" varied depending upon whether you were indoors or outdoors, and therefore had a different meaning than just saying X feet.
Right, but that variable meaning is irrelevant to the point. In either case, its giving you a scale to translate RW ranges into tabletop ranges.
This is an artifact of designing from a wargame basis, just as some modern designs unintentionally keep baggage (including spelling errors, etc.) from the 3e SRD.
It is an artifact of wargaming- one that implies that you're measuring distances between tiny physical objects that represent structures and beings.
So, if you're not using minis (or other physical placeholders on a grid) (or even if you are), that 1" is referring to a base number that must be translated to tens of feet or tens of yards, depending upon the situation.
Again, the differing scales between 1' = 10" indoors or 10 yards outdoors is irrelevant for the underlying point- in either case, they're giving you a scale to approximate RW distances for the minis on your tabletop.