Due to the fact that computers are very cheap, common and powerful, the
open-source hackers culture is essentially a "gift culture", as Anthropologists
refer to it.
Such a culture does not have a lack of resources, and its members do not need
to struggle to survive.
Instead, they are trying to increase their peer repute (which is by no means
fame!), and so are trying to make better impressions on their
peers.
This is done by producing or working on important open-source programs, which
are distributed without charge.