The Nevada Gaming Commission has one of the best reputations in the world. The vetting of licensed operators and employees screens out those with a history of unethical behavior. Licensing also encourages companies to operate legitimately through fear of losing licenses and or facing criminal prosecution.
Online gaming software must be tested for fairness. This includes the random number generators. Gaming sites must segregate player funds in separate accounts not related to operations. All bets must be paid in a timely manner.
None of these regulations apply to sites located outside of Nevada that operate without a gaming license. There is no reason to make bets at sites that are unlicensed in Nevada. A Nevada player giving action to offshore sites is at the mercy of an unlicensed company.