Ok, maybe not every country, but with at least 12 different sockets in widespread use it sure as hell feels like it to anyone who's ever traveled. So why in the world, literally, are there so many? Funny story!
The more you look at the writhing orgy of plugs in the world, the sillier it seems. If you buy a phone charger at the airport in Florida, you won't be able to use it when your flight lands in France. If you buy a three-pronged adapter for le portable in Paris, you might not be able to plug it in when your train drops you off in Germany. And when your flight finally bounces to a stop on the runway in London, get ready to buy a comically large adapter to tap into the grid there. But that's cool! You can take the same adapter to Singapore with you! And parts of Nigeria! Oh yeah, and if said charger doesn't support 240v power natively, make sure you buy a converter, or else it might explode.
And aside from a few oases, like the fledgling standardization of the Type C Europlug in the European Union, this is the picture all across the world.
I'd hesitate to refer to power sockets as a part of a country's culture, because they're plugs—they don't really mean anything. But in the sense that they're probably not going to change until they're forcefully replaced with something wildly new, it's kind of what they are.
What's Out There
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There are around 12 major plug types in use today, each of which goes by whatever name their adoptive countries choose. For our purposes, we're going to stick with U.S. Department of Commerce International Trade Administration names (PDF), which are neat and alphabetical: America uses A and B plugs! Turkey uses type C! Etc. Thing is, these names are arbitrary: the letters are just assigned to make talking about these plugs less confusing—they don't actually mandate anything. They're not standards, in any meaningful sense of the word.
And even worse, these sockets are divided into two main groups: the 110-120v fellas, like the the ones we use in North America, and the 220-240v plugs, like most of the rest of the world uses. It's not that the plugs and sockets themselves are somehow tied to one voltage or another, but the devices and power grids they're attached to probably are.
How This Happened
The history of the voltage split is a pretty short story, and one you've probably heard bits and pieces of before. Edison's early experiments with direct current (DC) power in the late 1800s netted the first useful mainstream applications for electricity, but suffered from a tendency to lose voltage over long distances. Nonetheless, when Nikola Tesla invented a means of long-distance transmission with alternating current (AC) power, he was doing so in direct competition with Edison's technology, which happened to be 110v. He stuck with that. By the time people started to realize that 240v power might not be such a bad idea for the US, it was the 1950s, and switching was out of the question.
Words were exchanged, elephants were electrocuted, and eventually, the debate was settled: AC power was the only option, and national standardization started in earnest. Westinghouse Electric, the first company to buy Tesla's patents for power transmission, settled on an easy standard: 60Hz, and 110v. In Europe—Germany, specifically—a company called BEW exercised their monopoly to push things a little further. They settled somewhat arbitrarily on a 50Hz frequency, but more importantly jacked voltages up to 240, because, you know, MORE POWER. And so, the 240 standard slowly spread to the rest of the continent. All this happened before the turn of the century, by the way. It's an old beef.
For decades after the first standards, newfangled el-ec-trick-al dee-vices had to be patched directly into your house's wiring, which today sounds like a terrifying prospect. Then, too, it was: Harvey Hubbell's "Separable Attachment Plug"—which essentially allowed for non-bulb devices to be plugged into a light socket for power—was designed with a simple intention:
My invention has for its object to...do away with the possibility of arcing or sparking in making connection, so that electrical power in buildings may be utilized by persons having no electrical knowledge or skill.
Thanks, Harvey! He later adapted the original design to include a two-pronged flat-blade plug, which itself was refined into a three-pronged plug—the third prong is for grounding—by a guy named Philip Labre in 1928. This design saw a few changes over the years too, but it's pretty much the type Americans use now.
Here's the thing: Stories like that of Harvey Hubbell's plug were unfolding all over the world, each with their own twist on the concept. This was before electronics were globalized, and before country-to-country plug compatibility really mattered. The voltage debate had been pared down to two(ish) which made life a bit easier for power companies to set up shop across the world. [Note: There are technically more than two voltages in use, which reader Michael clarifies rather wonderfully here]. But once they were set up, who cared what style plug their customers used? What were you gonna do, lug your new vacuum cleaner across the ocean on a boat? Early efforts to standardize the plug by organizations like the International Electrotechnical Commission (IEC) had trouble taking hold—who were they to tell a country which plug to adopt?—and what little progress they did make was shattered by the Second World War.