The answer is, in some ways, in the question. If the organizational structure is traditional, then it looks to the past for structure. This might be good, in the sense that it is time tested and it has worked in the past, but what if the situation changes sufficiently that new models are needed? The obvious answer is that models need to be adapted as well. The needs to be change.
There is also a cultural point of view. If something is considered traditional in one society and that organization moves to another culture, then structures may need to change once again. In short, one wants to keep an eye not only on tradition, but also on the future and how one may meet the challenges of what is to come.