My guess is that you're assuming all user defined types, and maybe even all non-trivial built-in types too, are boxed, meaning they're allocated on the heap when we create them.
That's not the case in C++ (the language in question here) and it's rarely the case in other modern languages because it has terrible performance qualities.
I think usefulcat interpreted "std::vector<int> allocated and freed on the stack" as creating a default std::vector<int> and then destroying it without pushing elements to it. That's what their godbolt link shows, at least, though to be fair MSVC seems to match the described GCC/Clang behavior these days.
Well if you're using the standard library then you're not really paying attention to allocations and deallocations for one. For instance, the use of std::string. So I guess I'm wondering if you work in an industry that avoids std?
I work in high-scale data infrastructure. It is common practice to do no memory allocation after bootstrap. Much of the standard library is still available despite this, though there are other reasons to not use the standard containers. For example, it is common to need containers that can be paged to storage across process boundaries.
