Because the Soviet system worked so well. AKA "We pretend to work, and the government pretends to pay".
If you would have a choice between USSR economic system and prospective collapsed civilization due to tech unemployment induced inequality, I am sure you would choose the former.
BTW, recent
NASA study looks very realistic IMHO!
That, my friend, is called a
False Dichotomy.
For the record: All civilizations that collapsed before were extremely centralized. Some of them, like the Easter Islands, directed all their ressources towards one goal, and worked "as one". Our civilization as it is can't collapse in it's entirety because it is still too de-centralized. Politicians are working hard to change that, but they are not yet there. We can, of course, have a world wide financial collapse - again, because the financial world is too interconnected and too centralized.
Interestingly, the problem of centralization and interconnectedness was entirely ignored in Jared Diamond's otherwise very interesting book "Collapse". Wonder why? It is the topic of Vernor Vinge's "Deepness in the Sky" and Dimitry Orlov's "Five Stages of Collapse". Interesting reads, all of them, for those who wonder why and how civilizations collapse.
Give me one historic collapse of a de-centralized civ (not conquest) and I will consider you less of a narrow minded totalitarism monger. What I mean is something like the Greek civilization. It never collapsed and in a way, it still survives.