My views in an earlier post in this thread are due to my cutting my teeth running Elric! Using the 2d6+6 for PCs, and 3d6 for NPCs rules I don't see as "cheating". PC adventurers should be a cut above your Average Joe. After all they're the ones fighting demons and bad guys to save average Joe's bacon.
Someone having a very low stat could survive, in a pre industrial society ( do you mean medieval?) with help from their friends. Low CON might just be the death of them if there was a plague though. As to becoming a functional adventurer, low STR characters could become spellcasters if their POW was high enough. Even characters with low hit points could take advantage of armour and shields, so it isn't as bad as it seems. We haven't even touched upon the subject of increasing stats through training...
Besides, adventurers tend to gravitate into groups that help each other.