Gameplay mechanics were also a lot better with more replayability.
Ignoring the lack of updates if the game is buggy, games back then were also more focused on quality and make gamers replay the game with unlockable features based on skills, not money. I can't count the number of times I played Metal Gear Solid games over and over to unlock new features playing the hardest difficulty and with handicap features, and also to find Easter eggs. Speaking of Easter eggs, you'd lose a number of hours exploring every nook and cranny finding them!
My games never came with a manual. Maybe because we swapped them in school shamelessly. Not needing to be online was a great bone because it made copying so much easier.