Mark Zuckerberg must have sensed a decisive win during Senate hearings last April the minute Orrin Hatch asked him how he turned a profit while keeping Facebook free. “Senator, we run ads,” Zuckerberg said, before issuing a cocky smirk. The remark (and the smirk) went viral, with Hatch and Co. mocked for their ignorance: doesn’t everybody know that advertising subsidizes ventures like Facebook, that being exposed to ads is the price we “pay” so we can access content without a credit card? That’s Capitalism 101!

Actually, I don’t know if it is true that everyone knows that. Ads are such an ingrained part of American reading life that we accept their presence in our media without question. As Julia Guarneri shows in her wonderful recent book Newsprint Metropolis (which just won an AHA prize), our big-city newspapers grew fat with fresh sections in the late 19th century because publishers needed to accommodate advertisers’ demands for particular types of news. Department stores wanted their ads to be seen by women shoppers, for example, so papers designed “woman’s page” sections to accommodate them. In the same way, advertising brought us the color comic strip, photography, the sports page, the advice column, the celebrity profile, the “local color” feature. As much as a daily paper helped give readers a sense of belonging to a place through what today we call content (including civic journalism), the ads also told readers who they were. Subscriptions and newsstand sales were vital to the paper’s circulation, but ads brought in the lion’s share of the revenue.

Advertising still subsidizes our reading today, but in the past several years publications have seen the revenue they have traditionally counted on siphoned off to “content distributors,” especially Google and Facebook. American readers still participate in the same invisible bargain: we agree to be exposed to ads in exchange for inexpensive content provided by publishers. Now, however, a new set of entities is profiting from our attention. And I don’t think you need to be an Orrin Hatch to be unaware of that.

The invisible bargain between readers, publishers, and advertisers makes it seem as though content accessible without paying a direct fee is free. It is not. It’s true that our online world includes no end of professional (or professional-quality) writing that isn’t paywalled or otherwise monetized. But the operating expenses of the outlets that publish it are usually underwritten in some other way. Perspectives, for example, always has a few paid ads, but it’s almost entirely subsidized by the AHA. A well-regarded blog might be unable to pay any of its staff or writers, passing its personnel costs along to staff members’ full-time employers and fundraising to cover operating costs. In other words, someone always pays for “free.”

This month’s wonkery is not coming from any great love for ads. Rather, people need to be paid. Writers, editors, developers, designers, photographers, fact checkers, and (yes) interns: they all need to be paid. You simply cannot have a free and independent press without participating in some transaction that in the end goes to outlets that produce what you read.

Historians and our colleagues in journalism might be sometime rivals, but both groups have concern for transparency in public discourse and a commitment to the accuracy of the public record. It’s my hope that we can help materially sustain a professional fourth estate, for our own interests and for the good of the future.