True, if the cops wanted to go as far as seizing my car they could, based on this video, but that would probably mean that they do it quite often or I am very unlucky. If they were stopping more random people and seizing their cars, who would they profile when they do this? Someone driving a nicer car so that they can "get more" or someone driving a Honda? Chances are that they would run into more problems if it was the former because wealthier folks will sue.
I would agree that some people don't have access to credit, but no access to a bank? Even if you live in the boonies, if you have cash and an ID, you will not be denied a bank account and a debit card. The only times I have had large sums of cash were, as you mentioned, selling a car or buying a car, but that only happened once every 2-4 years thus the probability of getting caught are low. Are the people in the video just very unlucky? Who knows.
Either way...pretty disturbing stuff...I've made that same drive from Elko to Reno through Nevada before...there's nothing out there.