Pre-3e editions of the game had a block of stats for each ability that changed according to tables, so even reducing them by 1 had an effect most of the time. The TSR core rules also have no mechanic to raise or recover abilities in natural ways, like by training, only some rare magical books or freaky fountains. This limits how many permanent magical items a wizard can create or how often a character can be raised from the dead. It also makes ability draining creatures quite terrifying.
