Partially because the socio-economic class of people who benefit from such tax laws overlaps heavily with the socio-economic class of people who create tax laws.
(Put another way: in "[1] economic theories about the use of [2] capital in a [3] market economy" there's a whole lot of assumptions and underpinnings, at least three of them, that are not laws of physics, but rather are ways of perpetuating and recapitulating our present system.)
The statement articulated two "parts" of the explanation.
The second "part" was phrased as a matter of class self-interest, with a critical tone.
But the phrasing of the first, as being "from" economic theories, can very easily be read as giving those theories a pass, esp. in environments like HN.
If we wanted to explain with some finality, we might answer, "why do we mandate lead shielding around radioisotopes" by saying the reason is "from physical and biochemical theories [about harm from ionizing your DNA]."
Or we might answer, "why are some traits observed to be epigenetic / both heritable and environmental" by saying the reason is "from biological theories."
The appeal to science-y authority is pretty conversation-ending in technically-oriented conversation venues like HN, I find. Or more properly, it might not end conversations but it makes that piece a leaf node.
I just like to remind people that economic theories are far, far more than their hard-science counterparts, political products.
Busting up trusts and forcing more competition is the best way to lower profits on risk.
20% (long term capital gains) of a million dollars is still $200k, so not sure why you would say they aren't paying taxes. Not to mention the sales and state taxes that rich people pay when they buy their toys.
Or is it just you somehow deserve the money more then them because they don't work hard / were born into wealth / are tax dodgers etc.
As an example: we got a "North American Free Trade Agreement" which allowed mostly free movement of capital between borders, but at no time was it even considered that labour would be able to freely move. Even for people like myself who are skilled in software, etc. it is quite difficult.
All of this is to reiterate what another poster said above: the people who control large amounts of capital have an outsized influence on the way tax _and trade_ laws are written.
If you were paid once every year instead of every week should both be taxed the same?