Tell me why

The biggest mistake C made by far was that arrays decay to pointers when passed through function, so buffers have to be idiomatically reconstructed inside the calls.
Remember that language idioms are just gaping holes from missing semantics, and C decided that keeping buffer size around was just not important enough.
I guess maintaining pure pass-by-value conventions was just too important.

The biggest mistake C made by far was that arrays decay to pointers when passed through function, so buffers have to be idiomatically reconstructed inside the calls.

What do you mean by "idiomatically reconstructed inside the calls"?

C decided that keeping buffer size around was just not important enough.

What's so hard about struct { void *p; size_t sz; }?