3 ideas
In Bug's case, a garage losing business to a corporate competitor and fixed family obligations like his mother's nursing home and his children's needs make one more illegal job look like a way out of slow legal failure. Money is the stated pressure, but the book also shows him drawn to the old life and turning down Kia's suggestions to sell the Duster or the garage, so the heist is a choice among options and not only a forced one.
Bug moves between Beauregard, the lawful husband and mechanic, and 'Bug,' the fearless driver he associates with his outlaw father. On the heist and in its aftermath, the skills he calls on to protect his family come tangled with the capacity for violence he fears he inherited and swore not to pass on, though the book also shows his driving put to purely protective use, as when he gets a woman in labor safely to the hospital.
In an economy where disputes are settled privately with guns rather than through institutions, every act of violence taken to protect a family creates a creditor who will collect from that family. The more effectively Bug uses force, the more exposed his wife and children become. Protection through violence works like a loan whose interest is paid by the people it was meant to shield.