Why aren't platforms treated as publishers?
Because most legal systems grant intermediary liability protection — services that host other people's content are not automatically liable for it, provided they meet certain conditions. This single rule shapes almost everything about how platforms behave.
The underlying logic. A newspaper chooses and edits every word it prints, so it answers for all of it. A service carrying billions of posts cannot review them in advance, and holding it liable for each would mean either shutting down or removing anything conceivably risky. The protection exists to make user-generated content possible at all.
How the protections work, broadly: the intermediary is not liable for user content it did not create, and — in most frameworks — loses protection once it has actual knowledge of unlawful content and fails to act. This is why notice-and-takedown exists and why speed of removal matters legally.
The crucial misunderstanding. People frequently assert that moderating content turns a platform into a publisher and forfeits protection. In the major frameworks, that is not how it works — protections were written specifically so that services could moderate without becoming liable for everything they did not remove. Without that, the incentive would be to moderate nothing.
What is changing. The trend is towards duty-based regulation rather than removing immunity: obligations to assess and mitigate systemic risks, to have effective reporting and appeals, to publish transparency data, to protect minors, and to give researchers access — enforced by regulators with substantial fines. The shift is from "are you liable for this post" to "do you have adequate systems".
The exceptions that already exist: copyright, with its own notice regimes; child sexual abuse material, where obligations are absolute; terrorist content, with very short removal deadlines; and advertising, where platforms are generally treated as responsible because they are paid.
Why it matters to users: it explains why platforms remove lawful content that breaches their own rules, why appeals are inconsistent, and why "free speech" arguments about private platforms misunderstand the legal position — community guidelines are contractual, not constitutional.
General information; frameworks differ substantially by country.