This is different though as they are using those scans to identify you with your identity (your passport details).
Maybe you don't travel very much or maybe you're a US Citizen but before I'm allowed to board a vessel headed for the United States I'm required to have an 'ESTA':
https://esta.cbp.dhs.gov/esta/If granted, this visa, or more properly, visa waiver program, allows me to board a vessel and enter the United States. Now without putting too fine a point on it, it's run by the Department of Homeland Security who have overarching access to all US agencies information and if you apply for an ESTA, what do you think the DHS does?- check my name, my nationality, my height, the colour of my eyes, my skin colour, my weight?
No, that 'identity' information is just the first stage of the checking process. The US already had all that 'checking identity' capacity in the Customs and Border Protection department. The DHS was formulated to link every piece of information known about a person, not just identity. Part of the rationale given for the creation of the DHS was to 'fill the gaps between the various existing agencies'. Recall that the
identities of the 9/11 bombers were known to US authorities before the attacks, it is other information that is required to make a full security assessment on someone, not just their identity. The passport, the SSN, the tax file number, etc are all ways for central governments to link non-identity information to a person's identity.
And no, I'm not paranoid at all. I'm quite comfortable providing details to governments to increase my personal security when I travel and, even when I'm at home for that matter. Just don't kid yourself that a passport is only about identity information and knowing who is crossing which borders; it's knowing who they are and knowing as much as possible about them to determine if that individual represents any type of threat and every piece of information that is available is linked to central identity documents like passports.
If it wasn't, how would a security determination be made? - "Yep, he's still the same guy, six foot tall, brown hair and has the same fingerprints". Doesn't tell you much, does it?