Yeah, their assumption though is you don't? Neither attribution nor sharealike, not even full-on all-rights-reserved copyright is being respected. Anything public goes and if questions are asked it's "fair use". If the user retains CC BY-SA over their content, why is giving a bunch of money to StackOverflow entitling OpenAI to use it all under whatever terms they settled on? Boggles me.
Now, say, Reddit Terms of Service state clearly that by submitting content you are giving them the right to "a worldwide, royalty-free, perpetual, irrevocable, non-exclusive, transferable, and sublicensable license to use, copy, modify, adapt, prepare derivative works of, distribute, store, perform, and display Your Content and any name, username, voice, or likeness (...) in all media formats and channels now known or later developed anywhere in the world." Speaks volumes on why alternatives (like Lemmy) to these platforms matter.
I mean, how do you do that for a closed-source model with secretive training data? As far as I know, OpenAI has admitted to using large amounts of copyrighted content, numberless books, newspaper material, all on the basis of fair use claims. Guess it would take a government entity actively going after them at this point.