Comment by AnthonyMouse

The incentive you're referring to is a law. The problem is that a primary entity you don't want tracking everyone is the government, and governments (like other entities) are notoriously ineffective at enforcing rules against themselves. The public also has no reliable means to establish that they're not doing it as they claim, and even if they're not doing it today, you're still rolling out a huge network of cameras waiting to have the switch flipped overnight.