Since nothing is holding the cartridge in a firm position if ignited the bullet and case would probably travel short distances in opposite directions. Storing ammo in steel ammo cans may actually offer some level of heat resistance and constrain any rounds that did ignite.
Remember in a house fire you have a lot of things that might be more dangerous, natural gas, propane, gasoline, aerosol cans and assorted other goodies.
A major source of objection to a free economy is precisely that it ... gives people what they want instead of what a particular group thinks they ought to want. Underlying most arguments against the free market is a lack of belief in freedom itself.
- Milton Friedman