because at that time, C creator didn't know thing would evolve into the future. after all computer is a new thing

Ok, but the question asks why one isn't made today.

There are many string libraries.

As you can expect, the answer to your question is the obvious one.

I do not think it is obvious or trivial question. I think the problem is mostly that there is no money for enhancing the C ecosystem and educating people about possibilities. The cooperate money goes into random new things.

I think most of the money goes to new languages that have a better strings story, yes.