And if you include BIOS (which is still needed if you want to boot a CDROM), that is four USB stacks - and you need a working USB stack at least to enter commands through the keyboard.
Probably the future is to remove the possibility to boot a CDROM and remove the possibility to enter a command at boot time or configure the BIOS, who needs that anyway?
Two weeks ago a friend came to me with a non working PC, the PC would not boot; his hard disk was not recognised by a live Linux CDROM distro neither. It was quite nice to be able to finally enter the BIOS setup, see that the HD was not recognised there neither (so the IDE interface was disabled), and finally diagnose that the rotating motor of the HD was completely dead - the disk plates will never turn again.
Soon, when your PC do not boot, the only solution will be to put it in the bin and go and buy another one.