While that is true, the only reason they aren't for alot of stories is because writers have human-centric thinking where humans are default and elves and dwarves are foils for different aspects of human nature. Humans mistreat the environment? Elves will be portrayed as the perfect society, where this never occurs. Humans are X, Elves are anti X. Under that mentality, there isn't any need to create diversity in fantasy races. Meaning the very idea that humans are better leads, or more exciting than fantasy races, perpetuates this problem of human centrism.
Well of course...we're human. The problem is that most fantasy races could easily be done with just a different human culture. It's just like with alien cultures in sci fi...most of them aren't really that alien...most authors simply can't create a completely different race. And it's understandable, because it's extremely hard.
That's not true because most fantasy races have a superhuman ability of some kind. Which means they're not interchangeable with humans in terms of using that ability to contrast the human condition. Example, elf immortality vs human mortality. It doesn't work with human immortality because that's an oxymoron. Immortality cannot be considered human. Otherwise you get the problem of human in name only. In which case it's another fantasy race. It becomes very difficult to introduce philosophical opposition on a racial level is both races are diverse. .