Personally, I don't get why Twitter is still popular and that a lot of casino really use it. It is full with bots and I really doubt if it is really so effective for marketing.
There are bots but at the same time real community as well so most of the promotions are done there.Moreover you will find the gambling community is active there while most of the other social platforms are not good and suitable for such promotions.They are getting attention from Twitter so it's going good for them.
With the popularity of a casino, they don't need to use bots because popular casinos have many followers willing to help spread their promotions.
And this is also used by influencers to provide info to their followers so that their followers can take advantage of the promotion.
The gambling community of a popular casino must be very active in sharing news or anything about the casino so it doesn't take long to find out.
And Twitter is still the choice of many of those casinos, even though it may be more advanced now than it used to be.