Bitcoin is not gambling and gambling is centralized, which makes it easy for some countries that banned it to reconsider lifting up the ban from gambling. They have cone to realize that it can be a source of revenue to the government.
As decentralized as Bitcoin, most people choose to use Bitcoin in centralized way, making it easier for government to take action.
The government can create their own exchange and force people to use their exchange, if they use foreign exchanges, the banks will freeze the money.
This also applies to gambling, Thailand do legalize gambling, but not all people are gamble in their casinos, some of them might gamble on unauthorized online casinos.