Back in the day it was simply the best option available. Java and Python only came out in the mid-90s and would take some time to catch on, develop a useful ecosystem, etc. And if you wanted to interact with system APIs, everything was in C. Nowadays there are much better options for a huge swath of applications. I would argue that--every bit as important as the language issues itself--one of the biggest reasons to avoid C is that all of its popular build system options are terrible. You're just expected to have the right dependencies installed on your system at the right versions and in the right locations (okay, some tools will try and find the location for various dependencies, but this is a pretty poor substitute for proper dependency management). And that's merely scratching the surface of the issues with C/C++ build tooling.
