Why Gurgjieff? Well he himself warns that his path is only for the thoroughly unsatisfied with the world's more well known paths, quickly speaking, the paths of religous, academic, or physical cultivation.
The way we understand his work here, it is not strictly internal. If you don't find changes in your external life then you aren't doing The Work at all.
My own personal reasons would be along the lines of the following explanation. There seems to be a flow for a person. If you go to with the flow (not that this implies not having to do some kind of work), you may end up a beggar, a soldier, a doctor, a family man or woman, or whatever. By flow, I mean a combination of things such as your family upbringing, your personality, your external circumstances such as the country where you live or the culture you find yourself in. If you are satisfied with the flow, there is no need to concern oneself with The Work. If you aren't and you want to go against this flow, then you will need unusual methods and tools. IMO Gurgjieff supplies these. Needleman gives a different perspective on similar methods in "Lost Christianity."