An insecure connection can be trivially eavesdropped (e.g. by your network peers, router, ISP or intermediate hops). Much of the time this will include identify

An insecure connection can be trivially eavesdropped (e.g. by your network peers, router, ISP or intermediate hops). Much of the time this will include identifying information such as your IP address and browser cookies. Consider reading medical publications or other personal topics and having that logged by an unrelated third-party. TLS adds significant privacy to your browsing habits, even when not transmitting data, per se. Edit: and, as others have said, the content can be modified by a man-in-the-middle attacker, which can inject fake content or malware.