Except they're not personal at all, being visible to god knows how many intermediaries and being recorded in plain text for any sysadmin to see. Maybe we'd like to treat them as such, and legislate accordingly, but that's not their inherent nature.

I think the problem here isn't lawmakers not understanding the implications of digital technology, but technologists adhering to a romantic view of technology rather than a literal one. Forget the law, forget the philosophy, just look at the mechanics of the process. Reading a web page is not a private act. It involves plain text communications over public networks through intermediaries to a host that is free to and does record identifying information. Privacy is not a core tenant of the internet protocols, whether you're talking about TCP/IP, HTTP, or SMTP.

This is not an example of an impedance mismatch between a technical term and the same legal term. We don't treat mailing addresses the same and e-mail addresses the same because they both have "mail" in the name. We do it because both have the characteristic of being routing information visible to third parties outside the communication. The idea is that routing information can't be all that "deeply personal" if you voluntarily expose it to a bunch of people. It's irrelevant whether its digital versus physical, or whether you call it "metadata" or something else, or whether the "bunch of people" is the postal service or your e-mail hosting service.