Passing containers by value or by reference

I am aware of the differences between pass by value, reference or pointer in the general case. However, my question is about special case about a container with simple structure.

Assuming this case:

class image{
    image()=default;
    image(image const&)=default;
    ~image()=default;

    int w;
    int h;
    uchar* data;
}

When passing an object of this class what copied are just two integers and pointer not the whole data. In this case is there purpose to passing it by reference ? Or is there a purpose to not passing it by reference?

The thing that triggered this question is that I have read that iterators in C++ were designed to be light and to be passed by value. So, I think that this concept may be applied to classes that represent a container to actual data no a data.