strncpy was never intended to be a safer strcpy. It was created for a very specialized use case in the Unix kernel--copying a string-ish identifier to a fixed-size char field that only uses NUL termination if the identifier is shorter than the field size. Because of how the C language and the Unix kernel coevolved, it became part of the standard C library by default. I've seen it used for it's original semantics in only a handful of places, but in general it's almost always misused.

To be clear, strncpy does not guarantee NUL termination. It takes a C string as the source argument, but it doesn't write out a C string; it writes out a very esoteric data structure that is unfortunately easily confused with a C string.

By contrast, strlcpy was intended to be a safer string copy routine: https://www.usenix.org/legacy/event/usenix99/full_papers/mil... In particular, it was designed to be what people seem think strncpy is. Its return value semantics are controversial, though mostly only among the glibc crowd as every other Unix libc, including musl and Solaris, now provide it. But the semantics were designed based on experience in fixing old C code, and observations about how developers tend to write C code, not based on prescriptive theories about how people should manipulate C strings in C code.