Si follows the songwriting tradition of Woody Guthrie which is finding that simple trenchant and memorable statement within his songs. " Aragon Mill" is an example.

Writing simple memorable songs is not an easy task. There are few today who can do this well. Steve Earle comes to mind.

Sometimes it's easier to write a complex, convoluted song than it is a song like "This Land Is Your Land".

Si, Woody, Earle and others have fused their simplicity and directness with political commentary which sparked the folk music movement (The Folk Scare) in the US.

I admire this kind of writing so much and would love for there to be more of it today.
I think that this kind of song lends itself to being added to and re-written in the folk process.

Woody at one time advocated the use of a song for this purpose. In the 60's, there was a push to copyright PD songs as variants to collect royalties. This may have had an adverse effect on the folk process. Music merchants don't like this approach. They may have a "Wall Street banker" attitude.