Well if the situation happens that people can't buy food, things will easily become nasty quickly. People will break open stores and use violence to get what they need. So cash money won't really help a lot in a serious situation.
The "civism" was well noted in the Spanish case, as far as I know, the whole country passed this incident without a single case of security issue. During the whole thing, people were extremely kind and polite. People sitting in dark bars was kind of "funny" how people clinging to their normal lives even in emergencies.
