Because they are all the consequence of holding it wrong, avoiding RAII solutions.
Working with native C APIs in C++ is akin to using unsafe in Rust, C#, Swift..., it should be wrapped in type safe functions or classes/structs, never used directly outside implementation code.
If folks actually followed this more often, there would be so much less CVE reports in C++ code caused by calling into C.
If I'm gonna write RAII wrappers around every tiny little thing that I happen to need to call once... I might as well just use Rust and make the wrappers do FFI.
If I'm constructing a particular C object once in my entire code base, calling a couple functions on it, then freeing it, I'm not much more likely to get it right in the RAII wrapper than in the one place in my code base I do it manually. At least if I have tools like defer to help me.
> Because they are all the consequence of holding it wrong, avoiding RAII solutions.
The reason why C++ is as popular as it is is in large part due to how easy it is to upgrade an existing C codebase in-place. Doing a complete RAII rewrite is at best a long term objective, if not often completely out of the question.
Acknowledging this reality means giving affordances like `defer` that allow upgrading C codebases and C++ code written in a C style easier without having to rewrite the universe. Because if you're asking me to rewrite code in a C++ style all in one go, I might not pick C++.
EDIT: It also occurs to me that destructors also have limitations. They can't throw, which means that if you encounter an issue in a dtor you often have to ignore it and hope it wasn't important.
I ran into this particular annoyance when I was writing my own stream abstractions - I had to hope that closing the stream in the dtor didn't run into trouble.