That's a British sort of thing.
There's also a distinction between 3-rail (commonly called O-gauge which traditionally was for toys/reliving the dreams of childhood) and 2-rail or "scale" which looks a bit more like normal track...and is definitely model railroading stuff. That being said, 3-rail stuff is used for modeling as well...as some of the stuff definitely rivals the best HO models.
The British layouts I've seen outdoors were 2-rail. They also have more options for Live Steam...butane fired steam locomotives in HO and O scale.