This is about having a technological means of making it non-beneficial to steal an item. Why would anyone be against that ? The police will NOT look for a stolen phone, well, unless it's a missing Apple prototype !!
If such a system were in place and a person tries to activate a phone that's been reported stolen, what would happen ? Would they simply refuse to activate it ? Would they quietly notify the police and keep the person in the store until they arrived ? My money says no store will want to get involved - they'll simply say "this phone's ID # has been reported stolen so we're unable to activate it for you. We're not accusing you of stealing it either...".