Why do we still need to know about the Rankine temperature scale?
Rankine is commonly used in the aerospace industry in the United States.

Rankine is to Fahrenheit what Kelvin is for Celsius. So when people in the United States were creating programs and using equations that needed an absolute temperature, they used Rankine before Celsius became dominate for scientific calculations. The reason people still sometimes use it in the aerospace industry is that there are a lot of programs that were developed using Rankine, so in order to be compatible with those old programs, it's often simpler to just use Rankine in the new programs too.

Thus, as an intern at NASA, I was writing simulations that used Rankine in 2009.