Having some word or phrase marking the end of a request makes the voice recognition a little more reliable. It doesn't have to be polite, but being polite when it's totally unnecessary is a good habit to build.
"Do X please" makes it unambiguously clear (to a machine) where the end of the request is, whereas "Please do X" is mostly pointless.
It's even sillier than that - 5x as much is 400% more. 399x as much is 39800% more.
I had to pay for a static IP just this week because it turns out the new ISP uses CG-NAT.
It's not quite that bad (yet...) - it has reasonably clearly labelled subscription and non-subscription cartridges. So when you cancel the subscription, you just throw the non-subscription cartridge back in.
If you're printing quite a lot, but not enough to justify a laser printer, then they can work out okay. The vast majority of people would indeed be wasting money though.
It depends on what you're building. If you want a normal rectangular house, 3D printing will be incredibly inefficient and pointless compared to traditional framing techniques.
On the other hand, if you want curved walls, traditional framing becomes incredibly complex and expensive, whereas 3D printing takes exactly the same materials and labour regardless.
I think 3D printing an entire house is just a gimmick, but it will still be an incredibly useful tool, even if only used for simple things like making rounded foundation pads or retaining walls that follow the landscape or curved hallways connecting modular buildings.