I don't do loose discs, full stop.
If you want to keep your disc in good, working condition, it needs to be in a case- why not the original? I'm actually pretty proud that my disc-based games are something like 99% complete... I don't have the map for Vay on Sega CD, and only one of my Turbo CD games has its outer cardboard box. But as far as the actual plastic CD case the disc sits in? I've got all of them. I've got nothing against those who prefer/are neutral to disc only- using a CD wallet, a spindle, or slim cases must save a lot of space. I'd just rather get some of that sweet, sweet box art to go with my game.
I went to a retro event last summer, and a friend bought a loose copy of Threads of Fate for PS1. He was saying he hoped it'd get home ok. I was confused: "I mean, it's in a plain case, right?" "no, it's disc only." "...so like a paper sleeve then?" "no, disc only"- and he proceeds to pull a disc out of his coat pocket. The guy sold it as literally disc only, no kind of protective cover at all. I was dumbfounded- I mean, you can get empty cases or paper sleeves for so cheap, who just sells a disc? Who BUYS it? I guess my friend! I immediately dug out the copy of Einhander I'd just picked up- "put that in here for now!" I don't like double-stacking discs in a case, but it beats just shoving the disc in your pocket. When they dropped me off after I gave him one of the empty jewel cases I keep on hand as replacements. That one really weirded me out.