This is not the case, at least here where I live. When I contributed to Wikipedia, we had a special page collecting copyright violations found by us. The "old media" section was terribly long, we actually had threads on our mailing list where people rejoiced that someone had printed the author and license information, as if it was strange and unexpected. Usually under stolen pictures they just wrote nothing, or "Source: Internet", which was even worse.
Printed media was also less willing to print an apology and/or attribution than websites, even when we specifically asked them to do so.
By "mainstream" I mean normal, non-crackpot outlets who are/were main distribution channels for information to people. In old business, major national newspapers, weeklies, monthly magazines, regional/city papers were fairly good at attribution. Of course plagiarism, stealing and other forms of non-ethical behavior were not unheard of, but not anywhere on par with new media.
Nowadays mainstream sources of information are supposedly replaced by swarms of bloggers and citizen journalists. This one is perfect example. Such a thing as non-attribution is now par for the course. You don't notice how common is it because you are not paying attention.
