Texas, a conservative state with a large faith-based community, has long considered gambling a vice, so the prohibition on casinos followed suit. Note: It's important to define gaming and gambling because they are two different things. Gaming is participating in legal, state-sanctioned wagering.
If you're short on time, here's a quick answer to your question: Gambling is illegal in Hawaii primarily due to the state's cultural values and historical opposition to betting and games of chance. Hawaiian leaders have opposed gambling since the 19th century, believing it leads to social problems.