Once upon a time, long ago, I rolled up a character for a one-shot adventure with a group of friends of a son of a coworker of my mom's. <insert Darth Vader/Dark Helmet joke here> I rolled my character using whatever their house rules for rolling characters were, and decided he'd make a good thief. "What's your Dex?" the DM asks.
It's a 16. That seems pretty damn good to me.
His comment: "Ouch!"
When I joined the 2nd Edition AD&D group, I rolled up a fighter with a Strength score of 17. I had arranged his other scores, as the DM's system allowed, and put the next-highest score in Wisdom, because that's how I imagined the character I wanted to play. No remarks this time, but every other fighter in the party had an 18 plus percentile strength, as well as superior Constitution and Dexterity, and my fighter's high Wisdom really didn't even out the odds much. He wasn't bad at all in combat, but the others almost always outshone him.
Some editions of the game just dispense with the ritual of random rolls altogether, and give characters maximum scores in their prime requisites. The implication is clear: A character with anything less is inferior, if not outright hopeless. Who would ever want to play someone who isn't absolutely awesome beyond the ken of mere mortals?
Well, I would, for one.
Some of the most beloved - and dare I say, compelling and interesting - heroes of novels and films weren't superhuman. Harry Potter didn't have 18 Intelligence. William in A Knight's Tale wasn't lifting boulders over his head. Bilbo was brave, and a pretty good aim with a thrown rock according to Tolkien, but I doubt anybody would read about him and think he had any higher than a 13 or 14 in Dexterity. Frodo's greatest asset was his Wisdom; in the abilities for which his classic D&D class is known (Strength and Dexterity) he probably wouldn't have rated more than 10 or so. I doubt even Aragorn had a single 18.
My point is that Average Joes are cool. Weaknesses are interesting. I liked playing my lowly enlisted man in a party of knights. In one of my games, he would have been exceptional without being a one-man world destroyer. Among a group of supermen, he was an underdog, but that just meant he had something to prove, as well as a humble identity to take pride in and try to hold on to. I don't even remember his name now, but I remember how I played him.
I think that the style of play that forces every character into the uppermost strata of the ability score scale just to be considered viable necessarily closes off the vast spectrum of tactical and role playing possibilities at the other end. Low and average ability scores aren't inherently unplayable, if you don't design your campaign to make them that way. Moreover, in a milieu where a low score is challenging rather than crippling, and an average score is, well, average, a high score actually becomes a valuable advantage, rather than a minimum requirement for survival.
I say, encourage your players to take up the challenge of the Average Joe. Play a thief with a 9 Dexterity, or a wizard of middling intellect. Embrace the philosophy that what sets player characters apart from the mass of zero-level NPCs is not their ability scores, but the courage and doggedness to take risks, face dangers, and hone their skills to advance in levels.
Now I almost wish I was on the other side of the DM's screen, so I could take on the role of the naive but determined farm lad with a Strength of 10 who dons chain mail and hefts a spear in his quest to make a name for himself....I bet he makes it, too, if he ever gets the chance.