I noticed that many countries use 4.0 scale for GPA scale, especially in the higher education (undergraduates and higher). There are also some other countries that use other odd/unusual grading scale like in French they use 20.0 and in Germany or UK they use 7.0 scale (CMIIW, I don't remember much).
But why did they pick these grading system (especially 4.0 in US)?
In many other aspects in our lives, the most common grading or rating scale is either 5.0 or 10.0 scale. And suddenly, in the academic system, they use other grading scale. It's even weirder considering in the high school and lower we used 10.0 scale, and then we suddenly switch to 4.0 scale at the university.
I cannot comment on the other systems, but germany uses a system that goes from 6.0 being the lowest, 4.0 being passing, and 1.0 being the best.
The swiss use a similar system, although inversed (so 1.0 worst, 6.0 best). For some reason, the 4.0 is kept as a passing grade, which leads to some shenanigans.