Fast, simple, low-level and relatively portable. The OpenGL API is in C as well.
We could spend decades elaborating on all the reasons why C++ is a horrible
language, but instead we will recommend a few related reads:
- The author of ZeroMQ, Why should I have written ZeroMQ in C, not C++ (part I) and part II
- Dorin Lazăr
- Linus Torvalds on C++
OpenGL is portable, mature and implementations are fast. Maybe it will be true for Vulkan in the future, but until then, OpenGL is pretty much the only option when targeting desktop and mobile.
It is very fast and simple to script in Python. Bindings in other languages could be added.