Having seen the "sausage factory" of consumer gateway devices myself, I can tell you the problem is not NAT or any other technology you'd like to blame.

The specs are written by non-technical product managers in the US, a contractor in Taiwan selects the OEM boards that most closely fit the spec requirements, pieces are combined and packaged in China with firmware outsourced to a completely different company in South Korea working off the OEM specs not the designs of the final product. (none of this is an exaggeration and is an example from a major broadband router maker)

They literally don't know if a feature works enough to print on the box until the first batch is unloaded off the boat.