The value of predictable chord progressions is that almost anyone can play along. This is community music, a different kind of art.

I myself like to sing more complex stuff, I like the challenges, but in a brand new setting, being able to recognize simple progressions allows me to sit in on songs I have never heard before. That has enormous value, and is true of most folk music I believe.

Lyrics are a whole other thing. The best lyrics are usually very simple, and simple is very hard to write. I can't write lyrics at all, even though I am a poet.