In practice, you need to learn the tax code to find most suitable form of conducting business. For example, in the UK if you know what you're doing, you'll pay ~20% tax on your income as a contractor. If you don't, you can easily end up paying something like 30+%.

Also, there are perpetual costs of having a company registered (such as monthly payments to an accounting company which handles paperwork, health care contributions etc.), so if you move around regularly between a couple different countries, you'll probably need to maintain a legal presence in each one, and thus have these costs multiplied.