Surveillance != Mass Surveillance. If you need to have an investigator show up in person to carry away a thumb drive of data about one case then this means you

Surveillance != Mass Surveillance. If you need to have an investigator show up in person to carry away a thumb drive of data about one case then this means you need to make a cost-benefit analysis about when to send out that investigator. If you can just go dragnet fishing and hoard data forever then there's no incentive to ask whether you really need to.