Imagine the pure joy a raider feels when wiping the dust away from a metal container and spotting for the first time a nuclear hazard symbol on the side.
The mind races with possibilities, considering who or what to target first. Perhaps the stubborn air craft carrier base holding three raiders prisoner or that coveted settlement with the massive garrison...
Scavenging
Though the wasteland is harsh and unforgiving, there is much scavenge from the ancients that can be recovered. Most of it is scrap (for turning into crafting steel), wood (for building up and fortifying your hideout), or garbage (for turning into plastics) -- but occasionally, one might come across the husk of an old world bomber or submarine.
Poking around inside might yield a rare surprise: a canister of napalm perhaps. Or a tactical nuke. Maybe some mustard gas.
Committing Atrocities
As your infamy rises in the wasteland, the local settlements will increase their garrisons and fortifications. When this happens, it might become too costly to attack without deploying siege devices or weapons of mass destruction first.
You could smash your forces against an impenetrable defense, but this would be suicidal.
If you have a tactical nuke or other weapon of mass destruction handy in your back-pocket, why not deploy that instead? You know you want to.
Committing an atrocity will clear a percentage of the garrison, depending on your success. With fewer enemies to fight, you should be able to successfully attack the settlement.
Use Your WMD Responsibly
Of course, this will have the adverse effect of raising your infamy in the area and causing other settlements and surrounding industry to further increase their garrisons and fortifications -- so be mindful of when and where you deploy one of these terrible (useful) weapons.
