Custom allocator in c++ for secure_string implementation not getting invoked

I'm developing a custom allocator for a simple and basic secure_string implementation in c++ based on https://en.cppreference.com/w/cpp/named_req/Allocator.

My code, as shown below, compiles and executes. However, I noticed that the allocate, deallocate methods of my allocator don't get executed. What am I missing?

static inline void secure_zero_memory(void *p, std::size_t n) noexcept
{
    std::fill_n(static_cast<volatile unsigned char*>(p), n, 0);
}

template <typename T>
struct secure_allocator
{
    using value_type = T;

    secure_allocator() = default;

    template <typename U>
    secure_allocator(secure_allocator const&) noexcept {}

    template <typename U>
    secure_allocator& operator=(secure_allocator<U> const& ) { return *this;}

    // define rebind structure for allocator
    template <class U>
    struct rebind { typedef secure_allocator<U> other; };

    T* allocate(std::size_t n)
    {
        std::cout << "Allocating " << n  << " bytes\n";
       return std::allocator<T>{}.allocate(n);
    }

    void deallocate(T *p, std::size_t n) noexcept
    {
        secure_zero_memory(p, n * sizeof (*p));
        std::cout << "secure_zeroed memory, deleting buffer\n";
        std::allocator<T>{}.deallocate(p, n);
    }
};

template <typename T, typename U>
constexpr bool operator==(secure_allocator<T> const&, secure_allocator<U> const&)
{
    return true;
}

template <typename T, typename U>
constexpr bool operator!=(secure_allocator<T> const&, secure_allocator<U> const&)
{
    return false;
}

using secure_string = std::basic_string<char, std::char_traits<char>, secure_allocator<char> >;

The cout statements above do not produce any output. Here's an example usage

    {
        secure_string ss = "";
        std::cin >> ss;
        std::cout << ss;
    }