For making their banner ads became more visible to gamblers it can possibly generate them more traffics and then revenues. That's why its good to see that they are expanding and this is good indication that they are serious for dealing to the gamblers here in forum and try to make their brand became more bigger. I also guess that everything they do here gives them positive result that's why they manage to expand to get more attentions from people here in Bitcointalk.
The more participants use this casino banner ad, the greater the traffic that is obtained, this exposure will be widely reached where many gamblers see this casino banner everywhere.
What's interesting about Rainbet is that this weekly raffle has the opportunity to win $ 400 with just a few tickets that you have, if you are lucky you can get it.
Rainbet also has a weekly race with a fairly large total prize, who is not tempted by this promotion.
So now there is a lot of attention.