Public screenshots? How you do you know they didn't pay for a media package/ rights?
Yeah, this. Also as mentioned above (they might be their own screenshots or they might be exclusives).
It's annoying when you're finding screenshots for a review, but it's not at all hard to find some good ones if you look around. If it's just for a topic or something who cares? If you're running a site you should have the facilities to get your own.
So yeah, what inspired this topic? It's totally reasonable they'd put them on there so their screenshots (whether one of the above reasons or not) can get them exposure. If they're hosting them then it's to be expected.