I think your idea of "bumps in daily use" is much more extreme than what the manufacturer is expecting. Dropping your laptop from ANY height cannot be considered daily use. So, even if you had the sleeve it probably wouldn't have protected it enough to NOT get damaged. It may have lessened the damage, but not completely prevented it.
That is the thing, I didn't drop it. It was a dent that could be prevented by having the sleeve. If anything, I had my ipod in my hand and literally smashed it into the ground and it was fine. My bag landed on my lap.