The software support went away, but also they stopped making drives (and controller chips) that can handle the 400K and 800K formats. Since they used variable motor speed on the 400K, 800K, and Superdrive (FDHD), they could keep a roughly constant flux density on the track. But when you try to read or write that on a fixed-speed drive, such as a 1440K drive in a PC, or any recent Mac floppy drive, the frequency required to match the flux density of 400K/800K disk format is outside the range that the drive electronics can reliably handle. Reading can sometimes be done, but writing is very problematic.