if as much engineering design effort had been invested in the plastic jewel* cases as the optical technology on the disc
Never mind the jewel cases. The real problem is the Cellophane wrappers, which seem to have been designed so that you need a scalpel to open them. Occasionally, rarely, they have a tear-off strip, which normally breaks off when you pull it.
There's nothing like buying a new CD and deciding to play it in the car. Numerous fatalities must have been caused by people bombing down the motorway while scrabbling at the packaging with fingernails and teeth.
* Why are they called jewel cases? They're totally unsuitable for keeping jewellery in, and I can't imagine that even the original designer thought a cheap plastic box looked jewel-like.