Why is “Agrobacterium mediated genetic transformation” in plants described as Natural genetic engineering of plants ?

Agrobacterium tumefaciens cause the crown gall disease  in most of the dicotyledonous plants. These bacteria contain large tumors inducing plasmid (Ti–plasmids) . A part called T-DNA of this Ti plasmid is transferred to the host which transforms the normal plant cells into tumor cells and directs them to produce chemicals needed by the pathogen . The gene transfer  and transformation is brought about naturally without any artificial methods thus 'Agrobacterium mediated genetic transformation' is said to be Natural genetic engineering of  plants.