I feel like this is an advertisement for that endless triangle shaped 3d printer with the belt bed.

Well to anyone outside the realm of 3d printer enthusiast they may be a cool gimmick to play with. But to anyone actually in it to only be able to extend the Y axis is somewhat meaningless.

Let's use your 4 ft pipe idea. On one of these printers like the CR-30 you could only get 4 ft if the layer lines run parallel to the length of the pipe. Not only is this bad for making an actual circular pipe but this is also bad for it's strength. Typically for a pipe we would want to print it standing straight up so each layer is a solid ring that layers up and builds a pipe. This will hold it's shape in a manner that can be reliably fit to other pieces and it will have better strength. But you can't get that on X or Y.

It's gotta be an endless Z to gain the attention of this enthusiast.