In an age where printed periodicals were delivered by subscription, the subscriber information was available (and yes, often tracked by local and federal law enforcement), but not the specifics of what articles were read.
Today, with Web-based document delivery and Javascript instrumentation, the specifics of who reads what articles, time on page, sections read, interactions, shares, and more, are available not just to the publishere but advertisers, any entities hacking into or accessing their systems, app developers, and more.
And, yes, law enforcement, whether under warrant, subpoena, or ... other methods.
Still, everybody on the street could see what we read while carrying the paper home. That can easily be dozens or hundreds of people. In some sense the periodic subscription via snail mail is in some sense the most private form. Sure, in the Web everything is tracked but in the average case literally nobody is aware of what we read. The worst case scenario can be quite bad though...