None of these, however, are as basic and-or intrinsic to the species as are stats. I've no problem whatsoever with each species within itself running on a 3-18 bell curve for each stat: Hobbits have their own 3-18 bell curve for Strength, as do Humans and Elves and Minotaurs. Cool.
If parties were always made up of a single species no adjusts would ever be needed.
But, the believability problem arises when you take those disparate 3-18 curves and try to compare them against each other in a mixed-species situation e.g. the typical adventuring party. Humans are the baseline and always have been, so the question becomes how does an 18 Strength (or any Str score) on the Hobbit curve map to the Human curve. Ditto for Elves, ditto for Minotaurs, and on we go.
To suggest that all these map out the same - that Str 18 on the Hobbit curve is the same as Str 18 on the Minotaur curve - is kinda ludicrous. And so, we get species-based bonuses and penalties to stats to reflect how they map on to that Human 3-18 curve. For the physical stats - Str, Dex and Con - I just can't see why there'd ever be any issue with this.
The mental stats - Int, Wis and Cha - might be a different matter; and maybe there all the 3-18 curves would map pretty closely to each other with the exception of the physical apprarance aspect of Cha: some species are simply more attractive overall than others.
