and there would be no precise numbers that you would really be expecting to look at but if you are really that interested on knowing it at least then better create a poll.
of course, this kind of poll will be biased and based on each user's preference here esp the casino they are currently promoting. the poll may be interesting to see but we already know which casinos are on the top tier and truly earning from this business. just look at the leaderboard or their stats and see how much money is moving in that casino. whereas, there are many small casinos which are trying to survive. also, there are various factors to consider and some of them have their advantage over the other.
leading casinos that we do have in the market today. Poll would be surely biased because they would be voting on those sites on where they had played on.
So it not really necessary which is actually true just like on what had been said above.