I always considered RPG's as a fantasy simulation with other rules. the ones provided by the game. does magic exist ? does space travel exist ? do parallel universes exist ?
You escape into another world with an rpg and therefore lack of realism is a disturbance. I think it's important. making the world believable within it's given rules is important for a good rpg.
examples:
- creatures that drop what they wield
- npc availabity depending on day time or in general go about their business (in the 90's game mags used that as a criteria for the quality of the rpg.)
etc.