I wasn't calling the orc's darkvision, "dim vision". I was refering to human normal vision. The human, who sees jack nothing immediately around him when the torch is a hurdred yards away.Yet even when the torch is a hundred yards away, the orc can see perfectly well in the area where he himself is standing; that doesn't sound like "dim vision" to me.
Let me put it another way. If you rename things so that elves have "normal vision," then the "normal" light radius of a torch is 40'. But a dwarf and a human looking at it can only see a radius of 20'. So the dwarf has "dim vision," like the human, even though he also has Darkvision (which isn't really dim at all).
And I just thought of something else, which is probably the real reason: D&D is just one game that uses the d20 system. In d20, humans are supposed to be the baseline, with no special powers or drawbacks, because not all games will have alternate races to compare them to. So even in a game where all the alternates have better vision than a human, whatever humans get is "normal" by default.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.