If these weren't songs commonly played on the radio, I would just chalk it up to popular imitating popular*.
Not "art imitating art". This isn't art; there's no real message outside of its marketable trite, and zero effort has been put into making these songs outside of some technical tropes (tropes that I hate, like Autotune, random Oscilloscope sound effects and irrelevant rap breaks).
Junk food might be edible, popular, and cheap, but it's certainly not good cuisine; nor will it ever be.
Mass-created media is always going to sound like samey-shit, no matter the genre.
Of course, I find 99% of pop-music to be shit anyway. I thought that in the 80s, I thought that in the 90s, and I doubt this trend is changing any time soon.
Why is it popular? Because of social pressure. Music is a network good (in economical terms); the more people who know others who like it, the more popular that song/performer will become, no matter how generic, annoying or boring they become.
Boy Bands were hot shit at the turn of the millennium, now it's the Autotune Hip-hop+Rap groups.
The real question is 'How long will it last until something else comes along and shifts the genre a little more?'