Yeah, but 99% of thefts don't happen like that. If somebody wanted to steal your macbook really bad, not even the old protection is going to help.
This is great for the 99% of thefts where you just leave it alone in the library while you say hi to a friend. People don't usually carry around metal-cutting scissors.
Obviously you aren't in their target market then, because locks are not pointless to users like myself. Sure cables can be cut, just like bicycle cables can be cut. When I am studying in the library and I need to step outside for a quick break or use the restroom, having that extra step of protection can be a godsend. Potential thieves will have to cut the cable in a public place, which is many cases can be a deterrent.
I hope you buy a better lock than the one that comes with. That is a very pickable lock. Thieves wouldn't have to cut the cable. Best option is put laptop in bag, go to restroom/take break/whatever and come back.