Because C has a huge user base. Yes it is a bit of a catch-22, but when I ask a question about C over on StackOverflow, I get the answer almost instantly. The same question about Python could take hours to get answered.

With respect to C++, it's IMO more complicated to learn. Furthermore, after having tried OOP for 10 years, I find it's not always useful, and often times it's easier to use procedural programming instead.