Even in 2015 it wasn't about keeping the copy unopened. Games came in CD but internet was barely getting fast enough to download large amounts of data fast and efficiently. However, CD has little collecting value or preservation qualities. They go bad fast, half of commercial CDs go bad in less than a decade. Organic layer CDs that were used for home burning are dice rolls. Only inorganic archival medium burned at very slow speeds theoretically can go for more than two decades, and it is still recommended to keep redundancies
On the contrary, I think it was, again, about convenience. CDs were part of DRM. A type of DRM that had to have the CD in the PC's CD tray in order to run the game, even if all the information was already locally installed. While later consoles acquired the capability to install the games to a hard drive for faster load times, this type of DRM was also adopted.
It was not rare for people to buy a game for PC, then immediately look for a crack online to play without CD. People were rigging hard drives to their consoles to install games there. Etc. So you could play your library without having to stand off the couch to change disks. Piracy offered the convenience at no cost.
That's not how you calculate car costs.
You only accounted for gas. Which is only part of the running costs. I also think that 46 mpg diesel is ridiculously optimist. Double check the source's numbers. They seem off.
What you do is count in the total cost of the vehicle and amortize it over your use case in a given period of time. Count in all running maintenance costs. This is the cost of purchase, plus insurances, registration, oil changes, scheduled maintenance and fuel. Over a period of time, divide by the total kms done or expected to be done in that time. That would be the real cost per km.
Do the same with the ebike and realize the difference is magnitudes more than comparing fuel and battery alone. Also, there is cualitative analysis to do as well. You're comparing an ebike, assuming it will be used as an electric motorcycle exclusively. An ebike with a dead battery is just a heavy bike, you can still pedal it. A car without fuel is a useless steel hull.
If you were to do the cost analysis this way to a plain old bike, even including food costs. It comes out to be virtually free, except for the most expensive carbon fibre performance bikes.