As Deksor said companies liked to use CD's even if all was used was a couple of MB. In fact Doom did exactly that.
Final Doom came on a CD, you can clearly tell by the files and the installer is was just using the 3? 4? disk images that ID had copied over to the CD.
so what that's a max of just under 6MB used.
Doom 2 was worse, that's definitely only 3 disks, but they rigged it so you could play the game direct from CD as well but NO ONE ever did that. Floppy, CD's etc are all slower then the HDD and speed was a premium back then.
So If you wanted you could do something similar, Install all the games to the HDD, then burn those folders to a CD, you could have like a 3d shooter CD with Doom's Duke3d, etc.
You wont be able to save games as CD's are read only, and you would want to configure any game settings as your locked in once you burn that CD.
And as already said NO ONE did this back in the day, I had a very limited space for quite awhile so could only have 2-3 games installed, the rest would be zipped up on a 420MB HDD with DoubleSpace compression (Would never do that now but it worked well back then). felt like playing a different game?
Backup saved games, uninstall, install game copy those savegames from backup.
But yeh as soon as HDD's became standard (386 era) all these disks/discs are like usb sticks today, yes you could play games off it, but you wouldn't, its just a method to get files from 1 place to another.