They don't want road checks for drunk drivers but then
    complain when a drunk driver kills someone. They don't
    want license plate scans for criminals and drug trafficking
    yet complain when they aren't caught.

I think the problem here is not that people don't want police to do those things, it's the belief that the power, once granted, will be abused. Drunk driving checks to catch drunk drivers are a good thing, but what about when a cop forces you out of your car because he didn't like your attitude? License plate scans are also good for catching criminals, but what about if the police store the data forever and tie it to personal IDs of people? Would you want the police to have a record forever of everywhere you've gone?

This is the problem with saying you have no need to. You assume you have already thought of every possible case when in fact, that's impossible to do. The most important part in the fight for personal privacy is in protecting the freedoms we have from potential abuse.