Answer:
Well, considering that radio broadcasts to the public began around the 1920s and was the prominent method to communicate news, information, and entertainment to entire countries' populations even after the introduction of television sets, radio broadcasting has had an "effective" track record. During World War I and World War II, every home had a radio, and families gathered around their one radio in the evening for news and entertainment.
Besides being the first source of news about threat of wars or beginnings of war (such as Pearl Harbor being attacked), radio was also how millions of people were duped into believing that aliens had invaded the world through a radio broadcast of a mini-theater presentation. Radio has alternately calmed-- or raised-- fears; incited-- or relieved-- panic; educated-- or kept rumors alive--about various topics; etc. Radio has informed people about health, disease outbreaks, international tensions, Presidential/world leaders' actions or plans; political arguments and debates, as well as providing entertainment through short plays, skits, live music (and much later, recorded music), etc.
Although television, the Internet, and cell phones provide the most instantaneous information, especially in informing "one family or person at a time", radio still reaches the broadest audience--- and the largest audience worldwide. As well, amateur broadcasters such as HAM Radio operators communicate worldwide and can share important information internationally, especially when or if other communication methods might fail.
Radio frequencies continue to be used by private and public ventures / companies, and the military of various nations use certain frequencies to communicate to and among their troops. Without radio, most of the world would become "silenced". In addition, in countries who forbid their citizens to get information directly (such as Communist nations), the citizens often do still get critical info and news by picking up international broadcasts with radios that the citizens have hidden. For examples, during WWII, Jews or POWs sent to camps tried to obtain a radio because information was power and with information, the prisoners could maintain hope. As another example, the USA deliberately broadcast on certain frequencies in the hope that Cuban citizens would be able to pick up the broadcasts; these broadcasts gave a different view other than Communism and helped Cuban citizens believe their lives could be different. It also helped politically when the US could broadcast messages of hope that were in opposition to Castro's iron-clad control over his nation / Cuban citizens.
Today, the "Emergency Broadcast System" remains the last defense and source of information during weather emergencies, and would be activated if the US were to come under attack. The EBS along with HAM Radio operators would be the sources of all information if radio or television broadcasting were to suddenly become disrupted (such as during an invasion / war on US soil).