I totally agree. And again I don't want to excuse their behavior.
But it being inconsistently easy to find a source and copyright information is also a problem that it would be nice to have solved. That there's a lot of variance in this process is itself a disincentive to engaging in it.
It would be beneficial for everyone if, in general, finding sources was as easy as finding the images to begin with. There's no in principle reason (or is there?) why technology has to make content discovery easy and source discovery difficult, it just is that way right now.
It sometimes is. Time and again, people have checked the pair's featured pictures and found sources in a few minutes.