Two train of thoughts. Making something 1:1 ratio is a true “macro” lens for photography. Because you’re increasing the size of the object to match the size of the sensor.
Then you got microscopes which makes things much larger than life.
For which manufactures call it what? Probably all marketing, but this makes the most sense in my life for justification.
Also Micro lenses are also used for marketing for CCD and CMOS sensors.