The main issue I think is having an active vs intert system as a data storage mechanism. A usb drive must interact with the computer in order to transmit data,

The main issue I think is having an active vs intert system as a data storage mechanism. A usb drive must interact with the computer in order to transmit data, a CD or DVD are ultimately inert disks which are read without any back and forth alterations. There is a higher degree of security inherent in that I believe. Unfortunately, the popularity (and honestly the convenience) of USB flash drives has made it hard to switch onto safer mechanisms.