> How does it explain soldiers, risking their lives and health for low pay and horrendous working conditions?
Soldiers defend their own families and friends against invaders who would kill or enslave everyone. That's perfectly reasonable, but it can also be considered selfish.
> People working on free open source projects
FOSS projects can be very interesting and rewarding work, not monetarily but in other ways (in excitement, reputation or maybe glory).
> People spending extra money on social benefits, such as fair trade coffee or electric/hybrid cars
Electric cars are better for the environment, and I imagine many people want a clean environment for everyone, themselves included.
> People choosing to be parents?
One reason to have kids is to have someone to take care of you in your old age (both materially and emotionally). Many people hate the idea of growing old alone.