I'm sure there are a lot of online cryptocurrency casino out there which are reputable even though they did not introduced their company here. But it is also my preference to play on casinos which are widely known here in Bitcointalk.
You see, many people choose a casino base on their reputation and because they have access to reach their representative from the forum here, believing that they have their signature campaign running on the forum here is another advantage gamblers decided to use the ones coming from this forum, other casinos out the forum here could also serve you right but incase of anything happens, can you trace or locate anyone of their representative or contact lines, people don't want to go too far without having a recommendation from someone they know that uses the casino and they also have interest in joining as well, every casinos on this forum had a discussion thread for their services.
Though it's true that it's better if you are using a casino that has a representative in the forum, I think casinos that are not present in the forum also do pretty well in managing customer problems if they are reputable and trusted and one should only gamble on a platform that isn't available in the forum if it already has a reputation.
A trusted and reputable casino, despite not having a representative in the forum, will be responsive through email and live support and I say this because I've seen it happening with myself in the past.