There are countless other benefits to having HTTPS (such as ensuring the end-to-end integrity of the communication so stuff can't be injected in the document). It's not meant only for private information.
Not using https means that your ISP, your mobile carrier, or your airport network provider can modify the information being presented to you. This is not a hypothetical, it happens all the time (though usually just to inject ads).
It's not about whether the provider wants the information to be public, it's about whether the provider wants the information to arrive intact.