Despite some of them now are made by computers (only in big cities), those guys are still in business. Demand for rubber stamp doesn't show any sign of slowing down. Take a look at your documents and you know why.
It is strongly advised that you should have one. It will be very useful in Indonesia.Use deliberately on your documents (or photo copies). Any documents (especially in English) with rubber stamp on it will impress some people. Always carry the when you plan to meet some local officials.
In case you are wondering what you should put on your rubber stamp, my humble advice is just put your boat's name on it. It is good enough, although boat's silhouette would be a nice addition.