USB 1.1 might be a terrible interface for mass storage (Firewire is great), but it's still useful in emergency situations. I also use a thumbdrive for moving files around, even on USB 1.1. It's faster overall than most other removable media, and most computers built since the late 90s have the ports.

Try finding even a modern *PC* with a 1.44MB floppy.

To say nothing of the space constaints. Apple got a lot of crap ditching the floppy, but they were ultimately vindicated.

Plus, the MacBook Air and a few other Macs (including the first and budget iMacs) have USB but not Firewire. Thus it would idiotic for Apple not to make the ports bootable.