Regarding "American adults engaged in business"....
I am sad to tell you I know many people who have been in business for years and STILL know so little about how the online world works. Using the default search is a feat much less choosing a search engine. Many still don't know they can actually choose a search engine, period.
The lack of basic computer proficiency clicking around Windows, copying and pasting files, saving files, using Word, Excel, etc. and basic typing skills is sadly still alive and well today.
Given this very low baseline that still exists to this day, it is not a far stretch that the issue of IP and copyright is extremely far away with many people.
You also have business people who naively hire overseas freelancers expecting ethical behavior but it turns out they pirate many elements of their work.
Let's remember, there are still huge swaths of people whose only Internet access is their phone. Some very small timers operate that way. Lots of "street entrepreneurs" out there who dabble online. When they eventually "graduate" to a computer, it is not surprising that there will be new people who fall into the trap.
And for the record, I find interacting with someone with such a low base of computer knowledge very painful to witness. And even people who are "intelligent", it is shocking the level of ignorance that continue to exist.
From my understanding the copyright notice has always been there. Furthermore, I think the reasonable American adult, especially one who is engaged in business, should have enough commonsense to know (1) Google is not a free library of images and (2) that you cannot just take and use what you do not own.