I don't know who you mean by "we" but most computer users (myself included) use USB thumb or hard drives, some sort of intermediate server, or network file sharing/transfer, to move personal files about.

Typical 120CM CDRs are dirt cheap compared to their 80CM counterpart. I have been using the few I have left for Linux ISOs.

Only if physical size is an issue would one use an 80CM CD (such as packaging with smaller hardware; I have a bag of 80CM CDs that came with hardware), if there were some reason not to have the files on the internet, or a thumb drive is uneconomical.

I am not talking about usb pen drives, this concept of my is fora cheap storage media like the good old floppy disks, a cheap cd/ cd r/w which costs a few cents holds a few mb of space.

Then a 120CM CDR is for you, if you want the cheapest, as those are mass manufactured, and the economies of scale allow them be produces cheap.

If you want something a little more convenient or portable than a 120CM CD, you have to pay for it, as not so many 80CM or business card CDRs are made, so the ecnomomies of scale dictate that cost more.