C++ why is noexcept required in the context of Move Constructors and Move Assignment Operators to enable optimizations?

Consider the following class, with a move constructor and move assignment operator:

class my_class
{

    protected:

    double *my_data;
    uint64_t my_data_length;
}

my_class(my_class&& other) noexcept : my_data_length{other.my_data_length}, my_data{other.my_data}
{
    // Steal the data
    other.my_data = nullptr;
    other.my_data_length = 0;
}

const my_class& operator=(my_class&& other) noexcept
{
    // Steal the data
    std::swap(my_data_length, other.my_data_length);
    std::swap(my_data, other.my_data);

    return *this;
}

What is the purpose of noexcept here? I know that is hits to the compiler that no exceptions should be thrown by the following function, but how does this enable compiler optimizations?