[Zirro]

Partially. I am old enough to remember computers with one floppy drive (for old software, explaining the A:-position), but too young to have experienced the times when you needed two.

[gutsy]

You never NEEDED two. All two did was make it easier to copy disks, and sometimes make it so you changed disks less often.

[agildehaus]

I'm from the time when A: meant 3.25" and B: meant 5.25", but you certainly didn't need a B:.