Why? They use it to compile a witness list, maybe suspect list, rule out many people, as a first approximation. As long as the data is archived and not open for abusive use; where do you feel any harm comes in?
How does this exonerate him if he has no lawyer to go thru the procedural efforts? You are right that hiring a lawyer is a choice, in as much as going to prison is a choice.
Because police would likely not even contact him in the first place once they see that there's nothing extraordinary about his movements.
This is plainly a type of General Warrant, something that was banned under the US Constitution