Why does a VertexArray use a vector<> to store the reference of a VertexBuffer, even though there is only one throughout its entire lifetime?

std::vector<Ref<VertexBuffer>> m_VertexBuffers;

I don't know if I missed anything? perhaps this container might increase to more than 2 at some point , or in the future?

I'm a newbie, please don't laugh at me : )