You may be wondering what's wrong with that. Surely having a beard is part of the very definition of a dwarf, just as being tall and ethereally beautiful is part of what defines an elf. But what I'm getting at with 'all dwarfs have beards' is one of the more unrealistic and frankly dangerous fantasy clichés: the notion that the members of any non-human race may be principally characterised by their homogeneity.
In fact, it's not the physical details that worry me. Every species has certain key physical characteristics: humans walk on two legs, eagles fly, dragons breathe fire. So as far as I'm concerned, the dwarfs can keep their beards. But with these physical details tend to come a host of behavioural and psychological characteristics that are much harder to swallow when applied to the species as a whole: all dragons are wise, all elves are brilliant archers, all dwarfs love their beer. And fantasy writers don't stop there. Some even generalise about their own species (does 'all humans are short-sighted aggressive destroyers of the natural environment' sound familiar?).
Part of the problem seems to be a confusion between cultural and personality traits. Different human cultures have different traditions, beliefs and moral structures, so it's reasonable to assume that different sentient species would too. The framework through which a dragon views the world, for instance, is going to be very different from that of a human. But cultural standards are not the same as individual characteristics. The point about cultural standards is that the individuals who share them can examine them, question them and deviate from them to a greater or lesser extent. Giving an entire species a shared personality trait, on the other hand, assumes that everyone who is subject to the same cultural and environmental influences will end up the same kind of person – and that's where authors go wrong.
It's perfectly plausible that all members of a religion might salute the sun each evening to ensure it rises the next day. It's not so plausible that all those members would be identical in their level of belief in such a ritual. Successful worldbuilding requires a careful examination and understanding of which features of a race or species are cultural, and therefore may justifiably be applied across the entire group, and which are individual and therefore can't. As I said at the beginning, not doing this is dangerous. Why? Because it leads to lazy characterisation based on stereotyping and generalisation. And just as we wouldn't (or shouldn't) accept this for different human groups, we shouldn't accept it for different fantasy races.