Just a hypothesis... Folks who are comfortable with the status quo will enjoy songs of love, praise, humor, heroes, etc. Those who are getting stiffed are going to sing protest songs. There may be an inherent bias toward song subject matter among different economic groups. Who would bother to sing...

My government is good,

My job is real fine,

I'm payed lots of money,

Play golf most of the time.

A documentary from back in the 70's called "California Riech" about a bunch on screwball kkk types had an interesting scene, these idiot losers were standing in the yard, one had a guitar and they sang a very jaunty, pleasant little tune with the following absurd lyrics...

WARNING!! OFFENSIVE MATERIAL!!!

America for the white,

Africa for the black,

Send them apes back to the trees,

Ship those niggers back.

Let the bells of freedom ring,

The white man's day is near,

No more nigger civil rights,

No more nigger queers.

America for the whites, Repeat. It was a very classic Anglo-American folksong type, the melody could be generic "rallying song".

Frank i.t.s.