Websites also offer 'terms' that you might never be forced to read (or actually read), but would still have some presumptive legitimacy in the absence of other customs: giving the site the right to curtail your use, or limiting your claims against the site. A court could reason, "What, did you think the service was free, with terms totally in your favor, in the absence of any other guidance?"

You might be able to argue ignorance/non-assent and then have them cease some objectionable reuse; you probably couldn't ding them for big damages because you thought you retained all rights.