They may not have a choice over that, but they may have had control over many of the decisions that led them into that situation. E.g. they could have chosen to study harder, to go back to school, not to have children when they lacked the money to support them, etc. They could have chosen to spend less money on consumables like cigarettes and alcohol.
I suspect this is particularly true in countries with socialised education/healthcare (most 'western' countries apart from the US). Most of the poor people I've met here in Australia, for instance, are either poor because a: they're happy with a low paying job, or b: they continually make bad decisions and have an anti-intellectual attitude, a distaste for learning and self-betterment. In my experience the ones who actively work towards improving their situation rarely stay in poverty for long.