I was saying "canned", not "boxed" or "containerized". It's a lot easier to write the little things yourself. (And there are good benefits to be had from writing specialized code yourself, instead of relying on big fat generalized tankers.)
I don't know what distinction you're trying to make about "canned" vs. other things.
There are advantages and disadvantages of using libraries in any language. There are some aspects of C —e.g. the lack of garbage collection— that make it harder to reuse code compared to some languages. But it is definitely not against "C's spirit".
I am finding it hard to believe that you think it's "just not in C's spirit to use canned libraries."