Mostly because of the general lazyness involved with music production and lyrical content.
The Axis of Awesome: 4 Chords Official Music Video - YouTube
AOA did a song with around 45 different songs that had the same chord sequence, I V vi IV. Although there are oldies I'd say around 60% are modern top 40 hits.
As for lyrics, here's two examples.
I can be selfish, be so impatient
Sometimes I feel like Marilyn Monroe
I'm insecure, yeah, I make mistakes
Sometimes I feel like i'm at the end of the road
I can get low, I can get low
Don't know which way is up
Yeah, I can get high, I can get high
Like I could never come down
Nicki Minaj - Marilyn Monroe.
Just generic stuff really. No deep, Simon Garfunkel esque meaningfulness here.
I can’t even lie, I **** better when I’m drankin,
Ride dick like a pro, throw the pussy like I’m famous,
Pussy feels so good, feels like the rubber off, ain’t it?
You ain’t gotta tell me, I know this pussy be yankin.
This pussy be yankin, I know this pussy be yankin,
This pussy be yankin, I know this pussy be yankin,
This pussy be yankin, I know this pussy be yankin,
You ain’t gotta tell me, I know this pussy be yankin.
Lady - Yankin.
Wut.