The disk drive can be used to read floppy disks using a computer connected to the disk drive. This is useful to get started, since the lower tier computer cases do not have a built-in floppy slot, and you'll need an operating system to boot up the computer. An OpenOS disk can be crafted using an empty floppy disk and a manual.
It can also be installed in robots to allow inserting floppy disks into the robot. This can be very useful since the only other way to transfer data to and from a robot is using networking - for example using network cards.