Some people like to deal with the imagined world from a character's perspective. From that point of view, it's not abstract numbers. Things have physical qualities, perceived via the five senses and with certain consequences. If they've got to choose between dealing with a situation in those terms familiar from real life, or dealing with it in pure game terms, they probably prefer the former. The two, they think, should be in some semblance of common-sense harmony. They're Alice, and dissociated mechanics are Wonderland.Personally, I look at the major objection in this thread to be confusing. I don't understand why an official fluff justification is really preferrable to having the freedom to choose whatever fluff I want.
A very simple abstract basis, such as in old D&D, is easy to modify in a more concrete direction. That's partly because of the lesser investment in rigid rules. 4E can give an impression of being more like Chess; that a knight moves always in an "L" pattern (rather than like a real horse) is a built-in part of the overall game balance, and that balance is given a high value by players. New D&D has a lot of rules, filling a lot of pages that cost (to some people) a lot of dollars -- with a lot more on the way.
So, people who put a premium on playing the latest version (perhaps because so many others are) may wish that it were more to their tastes. In the real world, of course, wishing does not make it so!