I guess most businesses couldn't care less about control over _all_ instances of the software they need to operate, but they want control over (and thus access

I guess most businesses couldn't care less about control over _all_ instances of the software they need to operate, but they want control over (and thus access to) every aspect of _their_ instance. copyright assignments are the standard way to achieve this (and then some, which they might not actually care about - but since it doesn't hurt...)