Airbags are only supplementary features to seat belts!
People should use airbags because they prevent deaths during car accidents.
As long as people sit properly in their seat, airbags will decrease the magnitude of injury. The combination of an airbag and the use of a seat belt provides the necessary protection for most vehicular related collisions, especially when many airbags work in unison.
It is better for the occupant to collide against the softer airbag than to strike the steering wheel or the dashboard.
Besides, no additional action is needed to activate airbags, compared to the need to buckle up seat belts.
Children however should not sit in the front seat as airbags may do more harm than good in this case.