Before record labels just tooo whatever the hot sound is abd repackaged it into a sellable image. Manipulative? Probably but nothing too evil.
Now with all we know about marketing from studies and corporation control of music they want to promote consumerism. But you can't just say "Drink Pepsi. Eat Mcdonalds" cause it's corny and people would recognize.
So they promote excess "party every day, all day,", lowered the vocab so that is accessible to even the lowest educated listener, and the image they crafted was no longer just cute but they had to look similar for recognizability from again the lowest educated consumer.
Also if you ever notice why the songs sound a like it's cause of bpm. If you want your song to be mixed with others and bring about the same feelings sonically you create them the same. So if I work at a record label and Taylor Swift, Zayn and 5th Harmony are all on my label and dropping singles in the spring I'm gonna make sure they all sound similar so it's easier to get in the audiences head.