So basically, the only reason to do this—acknowledged by researchers after more ambitious programs of this kind—is to reassure the public. It's theater, meant to calm irrational, emotional concerns. Unlike the TSA, people aren't even pretending otherwise!

To me, this is a great illustration of why we need strong, consistent rights and limitations on government action: it's not just a check on government abuse, or abuse by certain minority movements or even malicious abuse by the majority—it's also a check against popular emotional responses like this. It's a way of forcing ourselves to stop, reconsider and perhaps avoid acting poorly in a knee-jerk reaction.

(Also, thinking about it, it's a solid committment strategy: if these rights and restrictions are clear and unambiguous, we can use that when negotiating both with other countries and within our own government.)