You could try to design the tax code to try to distinguish people who were getting rich from zero-sum games, versus those who were getting rich from taking risks and creating wealth. In practice, there is a lot of subjectivity in doing so, and it would make taxes more complicated and unpredictable. In general, the more subjective and complicated government policy is, the more room there is for powerful and unscrupulous entities to manipulate the system to their own benefit. Complexity almost always favors the parasites.