[bradtemp]

It varies from country to country. 3 phase can let you send more power with the same copper, but it requires the connector be larger and with more pins, so there are arguments each way -- even in the countries where 3 phase is common. Most EVs don't come with onboard chargers bigger than 7-10kw, which can be readily done single phase, but is somewhat easier with 3 phase. But very little reason to use a 3-phase plug standard in North America. Only a few stations would provide it and almost no homes. Most people never charge at public level 2 stations.

[IshKebab]

In which countries is 3-phase power common?

[sschueller]

Switzerland and Germany, I have never seen a house in Switzerland that did not have 3 phases even very old homes.