Apple, Commodore, Osborne and others were using 5.25" disks at around or before the IBM PC came into play. IBM used 5.25" drives in the PC because they were inexpensive, reliable commodity hardware, much like the rest of the IMB PC.

I learned to edit on a Grass Valley that used the 8" floppies. It was the only real world experience I had with them. The only thing the system wrote to the disc was text based EDLs, and it still took forever. Get a cup of coffee slow. Best of my knowledge, there was never an upgrade for this, and it was still in use when I left in the early 2000s. This was at a time when NLEs were still considered offline quality only, and this system was used to do the final online edit from the tape sources.

And just to point out, the logical capacity of those disks increased with each physical reduction. Nearly doubling each time. (The best 8" disks had about 1/2 of the capacity of the worst 5 1/4" one, and the best 5 1/4" disk had about 1/2 of the capacity of the worst 3 1/2" one.)

I guess even if IBM didn't put it on the PC, everybody would migrate into 5 1/4" disks on almost the same timeline. Those changes were very compelling back then.

My first experience seeing an 8" floppy was a professor holding one up so I assumed it was a novelty educational oversized thing. They were ancient back then and it's been awhile since I was in school.

Even before then, 5.25" was popular among personal computer makers, such as Apple, Radio Shack, Commodore, Atari, and Osborne. (Though the TRS-80 Model II used 8".)

Wow, never knew that! Today I learned.