Three phase is useful for industrial motors or if you need more than 200A service. If I wanted to add another car charger in my garage and use them at the same time, they would have had to bring in another phase.

It just means that you can run industrial gear; maybe was owned by a keen potter previously. Big kilns need 3 phase power. No it isn’t common for domestic, but I have a few friends with big shed that have 3 phase power for machining tools.

Depending on what capacity the supply has; e.g. if you have a smallish 80A supply you can run a a good sized CNC mill in you shed.