So the B:\ drive is also for floppies... never knew that, i just thought the bigger floppies would just replace the smaller one...
Yeah. The early computers had no hard drives. You had one floppy drive, and that was it. Unless you spent another $1k or so on a second floppy drive, then your system was smokin'! If you only had one drive it was common to boot from one disk, put in the other disk with your programs and data, then run the program. Once the program finished, the computer would request that you reinsert the boot disk so you could use the command line again. Copying data from one disk to the other was a series of "Please insert source disk into drive A:... Please insert destination disk into drive A:... Please insert source disk into drive A:... . . ."
By the time hard drives became cheap, the "expensive" computers typically had two floppy drives (one to boot and run common programs, one to save data and run specific programs). And so it was common for the motherboard hardware to support two floppy drives. Since it was built into the hardware, it was thought that building the same requirement into the OS was acceptable, and any hard drives added to the machine would start with disk C: and so forth.
During the transition from 5.25" disks (which were actually, physically floppy) to 3.5" disks (which were encased) it was common to have both drives in one system, and again it was supported on the motherboard with hardware, and in the OS as fixed addresses. As very few systems ran out of drive letters, it was not thought to be important to consider making those drives re-assignable in the OS until much later when drives were abstracted along with addresses due to the plug'n'play standard.
