Why does everybody typedef over standard C types?

For the older libraries, this is needed because the header in question (stdint.h) didn't exist.

There's still, however, a problem around: those types (uint64_t and others) are an optional feature in the standard. So a complying implementation might not ship with them -- and thus force libraries to still include them nowadays.

stdint.h didn't exist back when these libraries were being developed. So each library made its own typedefs.