To put things into perspective - I am a trained first aider. I have the highest level of training possible without being a paramedic, and have been the head first aider at a few different places of business.
If someone falls ten feet, we have to consider a head injury and have to treat the patient as a head injury until we can rule it out. If a person falls twenty feet or more, we are unable to rule out any internal damage or head injury on the scene, and have to immediately call 911.
In other words, if you fell twenty feet, got up, brushed yourself off, we'd still be dialing the parameds, because odds are you're actually pretty banged up.
Does that mean that when I GM, I enforce crazy realistic falling damage rules? Nope, absolutely not - these characters get engulfed in draconic fire, get hit with death rays, poisoned, and everything else. Not to mention that it's assumed there's some weird stuff going on - the wizard survives a fifty foot fall due to casting a magic spell that takes off the worst part of the fall (he still takes "damage", but it's been lessened by an un-named spell or two as he fell). The Cleric and paladin don't die from the fall due to divine intervention, but still get a scrape or two. And that fighter or rogue doesn't die due to natural toughness and extraordinary training (and definitely a touch of luck).