Restrictions such as you describe only serve the interest of a small set of the opensim community -it's directly againts the interests of the majority of users.
Yes, everything could be locked down so that no one could do or share anything, but it's not desireable to do so.
"Just because you can do something, does not mean that you should".
Freedom of choice and openness is the better choice, there's enough closed modelling applications to serve the turbosquid level creators, while securing corporate, university and other grids can be achived on the access level (IE don't let any schmuck waltz in with a usb key).