I understand the Kardashev scale. I understand how (the various forms of) money are created and used in society. I am a member of United Economy, an alternative currency. I try to understand how thermodynamic laws operate, also within our societies. (the raw thermodynamic logic behind slavery in an agro economy) The concentration of power ((wo)men and money) to organise high levels of complexity. I understand how to use solar energy (active and passive, I built our own zero energy home and tried very hard to get my hands on thermal (salt) battery). I have a reasonable idea of where a fair and inclusive society should be heading towards (an economy for the common good, run on systemic consensus).

Should we want it....

....but the why we should still want it (to be hones) still evades me.

What thermodynamical purpose would that still serve? Most people have become superfluous, their brains and brawn better replaced by machines. So if seen from the bigger picture directing evolution, what purpose would your "Kardashev currency" serve? The only thing I can think of is the pacification of the masses. Rational logic would then link universal income to the voluntary abstention of procreation (like monks and nuns).

As for geothermal (or volcanic as you put it) its the time scale that matters. Our plannet and sun don't have endless lifespans either.