There’s an old email meme that you still see from time to time about how ancient Roman roads determined the width of modern railroads. Snopes tells us that it’s not terribly accurate, but the moral is clear enough: precedents are hard to shake.
Some patterns, like which side of the road you drive on, are very coercive. In such cases, once a local pattern is established, it’s dangerous or impossible to oppose it. What’s interesting is when these local patterns grow from small seeds into a global mosaic. Coercive growth of left-side driving, for example, propagated through much of the British Empire. But frontiers between differing regions are interesting places. What happens when you drive your car from a left-driving country to a right-driving country? In some cases (like Sweden in 1967) the resulting friction is enough to make the whole country switch. But in general, the cement has hardened, and everybody just has to live with the tension between two standards.
Electrical plugs are good examples of this. The standards are coercive, and when they harden, there’s not much you can do after that. Here’s a good article on Gizmodo about Why Every Country Has a Different F#$%ing Plug.
There’s a nice bit in there about how the UK came up with a new plug design after World War II. It seemed like a reasonable time to try something new, and the UK had a whole empire to foist it on after all. So you can see why they felt a certain sense of entitlement. But their timing was, in fact, terrible. They acted at the very moment the empire was going to pieces, and the legacy is an electrical plug that works (almost) nowhere else in the world. Still, what a manly hunk of metal is the English plug! It certainly shames the effete French two-pronger across the Channel.