The Ideal splice they are talking about is advertising this is perfect for "prefab" boxes. We may be buying boxes directly from China with the devices already installed. Snap them around the framing, push the wires in the splices, shove it all in the box and snap in a "button". Off you go. The only tool you need is the one you strip the wire with. Maybe they will come out with one that strips the jacket and both wires in one step on a 12/2 or 14/2 Romex Scary huh?
IMHO, the method installed (pigtail or feed-thru) is the installers option & choice.
Some of us prefer to pigtail at each location, some of us may be looking for that 'little labor & material cost reduction'. As there is no mandatory reason to pigtail in all situations (Yet), the choice is the installer.
In Austria or Germany I never pigtail unless I encounter a seriously overfilled old-work box, for a very simple reason: box fill doesn't allow me to have any kind of connectors AND a device in a regular dephth 58mm box. If I have some old masterpice with more than 2 cables I don't have the coice, I have to pigtail because modern receptacles won't take more than 2 wires per terminal. I'd say that's a grey area then. In Germany it's worse since the standard box there only seems to be 40mm deep instead of the 50 we have in Austria. Deeper boxes exist, but are very rare, at least in Austria (haven't seen them in shops yet, except one very expensive electronics retailer with mostly German stock). Those 50mm deep boxes are barely enough to take a Schuko receptacles and 6 4" long 2.5mm2 conductors. Getting 9 1.5mm2 conductors + connectors + pigtails + receptacle in there is a major pain.