Harley wrote:
One might argue that they are 'tubes', not pipes, not that most people would know the difference.

Harley even water mains and sewer mains etc are tubes by definition as the external diameter is fixed even though they are sized by a nominal internal diameter. This is so the fittings are common. As the pressure rating of the "pipe" goes up the internal diameter goes down while the external diameter is fixed.
Although what is now Tyco used to be called Tubemakers, most people in the industry still refer to the tubes as pipes.
I reckon this sort of thing is like the Americanisation of Australian culture.... over time some things become less important to the general population and only the dinosaurs among us care.
Hope you all had a great weekend.