hi i think this could be the reason These USB
connectors let you attach everything from mice to printers to your
computer quickly and easily. The operating system supports USB as
well, so the installation of the device drivers is quick and easy, too.
Compared to other ways of connecting devices to your computer
(including parallel ports, serial ports and special cards that you
install inside the computer's case)When the host powers up, it queries all of the devices connected to the bus and assigns each one an
address. This process is called enumeration -- devices are also enumerated when they connect to
the bus.