They say modern songs get written by a huge group of songwriters in hotels. Individual words and phrases will earn credits. They go through the list of everything floating in the songwriters' heads and whittle it down on a huge whiteboard and anything put up there and put into the song gets credited. I think the phrase they used to describe it was "Shit Smoothie Song Writing."
The person I know hates this and doesn't work with these people but they know the industry, etc.