Power transformers were required in receivers in Canada until they relaxed the electrical code requirements due to material shortages during WW2. I don't think the lower mains voltage had much to do with it, because the US has the same 120V mains voltage and they made a lot of AC/DC 5 tube receivers using the 35Z5 (and later 35W4) half-wave rectifiers. After the war, the cheaper transformerless receivers became popular here. But the high end receivers continued to use power transformers and fullwave rectifiers such as the 5Y3, 5Y4 and 5U4. Almost all of these high end receivers also had push-pull output stages which were good for cancelling out hum.
I agree though, that the transformerless sets with halfwave rectifiers did hum unpleasantly. That was the tradeoff for a cheap radio.
I still build a lot of tube circuits for fun, and have never yet needed a regulated supply. I'm not saying that regulation is never required, but people just naturally assume that regulation is always required, when in many (if not most) cases, it's not.