I know you mean software applications, but another very common application of C is almost any device that uses a microcontroller unit (which is probably dozens of things you own right now). It is incredibly adept at interfacing with processing units at a level close to the metal.

That’s also why you’ll see OS kernels and low level system tools and libs in C as well. It provides a good balance of functionality and abstraction so you can scaffold from register manipulation and interrupt functions up to high level code very quickly.

It also provides a good application binary interface (standards of interoperation with other languages) so you’ll find a lot of applications may be written in C++, Java, Python, etc. but they use a decent amount of core functionality implemented in C.