Well, people stealing gas would be a rather moot point, at this point considering that vehicles are aparantly rundown and that it would be a rarity to actually find a already full resevoir of gas. And Marilyn Monroe is too cheerful, moreso in that song.
Fallout One's intro was pretty shocking. In the background, you've got the Inkspots crooning "Maybe". The song "Maybe" is wistful and at least melancholy. All the while, you've got Brotherhood men executing a prisoner. Then the intro fades out from a television screen to reveal a shattered city and the song stutters.
Fallout Two has Louis Armstrong's throaty and powerful voice singing a song of reminsence. And the song is accompanied with a humorous pseudo-instructional film long remembered in the 50's era.
My point is that both Fallouts had easy, set-back songs from the 50's that filled people with either the feeling of hope, lost, and rememberence. At the same time, the visuals are in stark contrast with what the world has become or about to become.