I guess it's for colloquial understanding and conversion more than anything. Nobody refers to a corner as a pi/2 angle, they refer to it as a 90 degree angle. Unless a person specifically studies mathematics, they're likely to never hear about radians in their life.
It's a manmade concept to describe a natural geometric relation. The factuality of it held true before its introduction, but it didn't exist as an idea until a mathematician developed it.
So I suck at math, right? I just finished a semester of Calculus, and I had to see a tutor to prepare for the final exam. He zoomed past a limit form of the derivative problem like it was nothing, and for some reason when I found out that the sqrt of something was just that thing to the 1/2 power, it blew my ******* mind. I passed the class with a 70% exactly
Wait! You've taken calculus and you didn't know that roots are 1/x powers of something? **** I learned that two years before I even went to uni. Then again my school was kind of math focused.