C and some limited amount of assembly are what drive most of the electronics that surround you; most of the of "smart" devices in your house, car and pocket contain large amounts of code written in C. The phone infrastructure you use, the traffic signals, the network you get news from, the browser you're using right now? C.

Scripting languages and bytecode-driven languages? Their interpreters and jitters are likely written in C.

There are exceptions. I understand that some Java-based systems are built in Java, all the way to the metal. Apple was a Pascal shop until it turned to C in the late 80s. By and large these are systems on the fringe, and the bulk of the heavy lifting today is done in C.

You should probably understand it.