In much of the world, radio stations were located only in the big cities. In rural areas, listening to local "tropical band" SW stations was very common, and there were many, many stations. All over Africa, the Middle East, Asia and Latin America there were many, many SW stations. They were listened to both locally and in rural areas where there was often no telephone service and of course no radio station.
International shortwave began in earnest in the 30's and was a popular way to hear entertainment and news from other parts of the world. It was extensively used in WW II for propaganda by both sides of the conflict. And then, the Cold War caused many countries to broadcast their preferred ideology. Other nations promoted their culture and tourism via shortwave.
In most of the world, radios had SW and AM. When FM started growing in the late 60's outside the US, more and more people wanted FM radios and manufacturers traded FM for SW on their products, so SW began a slow fade over the next 30 years.
To better explain the demise of shortwave radio, you have to understand that the SW medium had long been divided into "domestic" and "international" broadcasting, each of which had their separate timelines into oblivion.
Domestic shortwave broadcasting was targeted at its own country, or a region of that country. Government broadcasters in much of the world used it to serve areas of the country beyond the reach of big-city based AM stations. In Latin America, there were hundreds, perhaps a couple thousand mostly private broadcasters that used SW to extend their coverage. Most were simulcasts of AM stations, but there were some that were SW only.
I started listening to SW in the mid-1960's, when the bands were chock full of domestic SW broadcasters. Hearing local output meant for the citizens of a particular country or city was a totally fascinating window into different cultures. But by the mid-1970's I noticed that those stations were starting to thin out and disappear, as the expansion of FM transmitters, and the increased availability of affordable and decent quality FM radios, was drawing away the former SW audience. This trend steadily continued for the next several decades, until the point today where there are very few domestic stations left on SW. In Latin America, Brazil still has a considerable number of SW stations (somewhere between 50 and 60) while Peru has around two dozen (both those numbers are way down from the peak decades ago.) Bolivia still has a few left, but elsewhere in LA the medium has disappeared except for a few stragglers.
The decline of international shortwave broadcasting came much later. The 1970's and 80's was a time of great expansion of broadcast ouput, with many new languages and transmitter facilities added. But by the 1990's the advent of satellite delivery and cable television started to chip away at the audience, and broadcasting schedules and language services were steadily trimmed. The end of the Cold War also lessened the need for propaganda broadcasting. The real death blow came after 2000 in the form of the Internet, when information filled web pages and audio streaming made SW virtually irrelevant. Lots of countries eliminated, or at least sharply reduced SW output, and many transmitter sites were closed.
I'm glad I got to listen to SW during its heyday; as a young person it really brought the world to me, with different cultures and perspectives. I have very fond memories of that time, but I am also the first to admit that SW is virtually dead, replaced by better technologies. Perhaps decades from now we will look at our current computers and smartphones the same way we now look at those old vacuum tube Hallicrafters and Heathkits.
