Making an Island/Motivations
There are probably some laws that you do not agree with in your home country. For example, in the U.S., to drive a car in most states you would have to pay $1000-$2000 a year in car insurance. If you created your own island outside claimed territorial waters, you would be able to enact your own government. Along with the benefit of likely not needing a car on your own island, if you had an island big enough to need cars, you wouldn't need automobile insurance.
When you create your island, you can base your government on those already in place, with your modifications to the current systems, or devise your own system. You could base it on historical models, like the Roman triumvirate, or you could take it from a theoretical system, such as that in Thomas More's Utopia. With your own island, you can change the government so that you are the government.
If you have limited funds, cannot earn enough money to survive, or simply cannot find a job, building an island may be right for you. Provided you live near a body of water, you can build an island which has shelter, food from fishing, and a possible income generating potential in the tourists that would come to visit your island.
There are also many ways an island can be utilized to generate both raw materials and energy. The sea can be farmed just like ordinary land, only the products are different.
There are some people who for reasons not entirely under their control have been denied citizenship in all countries of the Earth. People who are in this position literally have no where else to turn; however, it could be argued that people who are in this position are also incapable of gathering the resources necessary to build an island.