Probably because where C++ is needlessly complex, C is beautifully simple.
I've used both C and C++ in my career, spending 10+ years as a C programmer (kernels, applications and embedded stuff), as well as 4-5 years as a C++ programmer in a financial institution.
I find the thing most "new C/C++ programmers" complain about is memory management and type safety, but honestly, once you have a few years worth of experience, memory management is almost second nature. Most of the time i write the free() statement at the same time as i write the malloc() statement (if applicable).