The metaphor "roots", in relation to music and song is a useful one, but like all such metaphors it can be a trap when it gets treated as if it was a literal statement of how things are.

The trap is the way it tends to get interpreted as implying a doctrine that a musical tradition necessarily has one origin - so "is rooted in the dispossession of the working class etc" is taken as meaning that this is the only source of traditional music.

That pretty evidently isn't true - but that doesn't mean that this dispossession etc hasn't a very significant agent in shaping and transmitting the folk music which has come to us, because that is pretty evidently true. Not just songs of conflict and struggle either, but a whole range of songs - collected from old farm labourers trapped in workhouses in their old age, for example.