The vast majority of all code you write will not invoke UB, most people tend to stick to an 'easy' subset of syntax, unlike say C++ where everyone uses a different subset of features making it in effect multiple languages.
A combination of testing the known edge cases, wraparound issues, size issues, static analysis and tooling means running into an example of UB is extremely rare in most cases.
It used to be that people used dynamic memory allocation to beat C with, but that is just a resource management issue. TBH, this is not rocket science. If you need dynamic memory allocation, you had damn well better know how to use it properly.
Its an example of laziness and people ignoring the machine.
Another example is performance; saying that a language comes within a factor of 2 of C's performance and therefore is fast is absolutely ridiculous. a factor of 2 is huge.
You have to remember that people who write C are dealing with machine-specifics day-in, day-out. we're bit-fiddling and writing MPU code and drivers, etc.
Basically, we're much more aware of the machine than higher-level softies, so what would normally be UB is actually DB in most cases, its defined by the compiler and hardware that we're intimately familiar with.
...and that isn't to say that you can't write high level abstracted code in C, the simplicity of the language lends itself to (properly) efficient implementation, not efficient in the sense of Java or Ruby ;o)
