I would have to go retrace some reading pathways from a decade and more ago, but my memory suggests that the "burning" potlatch was only observed after Anglo conquest of the Pac NW and sustained attempts to wipe out the first nations' languages, religions, and cultural patterns.  the ethnographer whose book I was reading at the time was of the opinion that the "burning potlatch" was a debased or corrupted form, inspired by the despair of the tribes as their land was stolen, their children forcibly taken from them and "re-educated", their sacred sites demolished or profaned, etc.   s/he read it as similar to the self-immolation practised by some Asian peoples as the ultimate statement of shame, grief and rage after defeat by an overwhelming force.

the destruction or sealing-away of goods in an intact culture is iirc more strongly associated with organised hereditary kingship, like the grave-goods of the pharaohs.  he who dies with the most toys tries to take them with him into death, selfishly ensuring that no one else will have any use or benefit from them.

The difference between theory and practise in practise ...