If I may propose a different explanation:
Many people vote against measures that are supposedly supposed to help them---universal healthcare, larger tax credits to the poor, cash welfare---because they think "why am I giving $15000 to the Feds when I can barely afford it, and they're just going turn around and give some of the money back but with strings attached".
I think that framing people's political opposition to measures that you support as "voting against their own self interest" isn't helpful because it alienates the people you're trying to convince. Even if you might not think that opposition to universal healthcare, or tax credits, or welfare, is rational or sensible, that opposition may be rational or sensible when viewed from the perspective or someone else.
There is a certain appeal to self-sufficiency that doesn't have to spring from radical individualism. It's extremely stressful feeling like you're not in control of your own life. Globalization and computerization have increasingly centralized power in either corporations or national governments. Some of that loss of control is political; for example, the steady erosion of the first sale doctrine under the guise of protecting "intellectual property". Some of that loss of control is due to the advance of technology, and can't be undone without further technological development; for example, barring significant breakthroughs in at-home manufacturing technology, your average consumer isn't going to be making an x86 CPU in their basement. Increasing people's ability to be self-sufficient should be something we can rally around as technologists---reducing healthcare costs so individuals can diagnose and treat themselves for common maladies, reducing the capital needed to manufacture modern electronics, increasing transparency and access to knowledge so people don't feel trapped by seemingly Kafkaesque bureaucracies and organizations---and I feel that trying to focus on common goals is more likely to result in positive societal change.