I often wonder if low cost thyristors existed in the first half of the century to produce buck and boost converters if the electrical grid would use direct current. High voltage DC doesn’t suffer from impedance, although it is more dangerous to touch as there is no zero point for seized muscle of a human to release themselves from it. High voltage DC is also much more difficult to break with a mechanical switch, due to a lack of zero point to prevent arcing, which is why they usually use thyristors rather than mechanical switches to break DC current.