Someone Somewhere :
Firstly, why?
And secondly, the calibration in those is usually hopeless, so efficiency and power measurements are massively wrong.
Well, I'd like to have that kind of information. It certainly isn't a necessity, but it is good to know how much power your system is actually drawing. For instance it would help me determine how much power headroom I have on my UPS before it becomes unreliable. It could also lead to smarter cooling systems that counter heat increase based on heat generation instead of temperature.
As for being wrong, they don't
have to be wrong. On a PSU, that would essentially mean a PT and a CT connected to a microcontroller with analog inputs. Calibration can be done electronically in production line. Power and other electrical readings are actually much easier to calibrate and achieve decent precision than thermal readings.