>>96324478
First reason:
* Dwarves are strong, they don't get sick or weak
* Dwarves are stubborn, they refuse to die
* Dwarves are greedy, they refuse to give up life

Second reason: in most fantasy settings, you need a plausible explanation why humans are like 80% of the population. Most common one being they're like rats: breed like fuck and swarm all over the place. Short lifespan = massive population, therefore the inverse must also be true. (That's also why Elves tend to despise humans. Human:Elf = Termite:Homeowner

Third reason: because Tolkien did it and most fantasy worlds are just ctrl+c/ctrl+v.