I have seen several casinos with promotions where they do "drops" to thousands of people or they give bonuses to several gamblers, but how transparent is this process?
Do you think casinos are really doing these drops to 1000s of people or are they skimming from the top.... ? They might say a drop is for 2500 people, but they might only drop for 500 people and nobody will know. Yes, some of those 500 people will report that they have received the drop and it will look legit.... but is it really?
How can the gamblers verify that the actual amount of people are receiving the drop or the bonus, if there are no list to verify it? Let's discuss this.. I am curious if other people also thought about this...

Check it probably still impossible, but there are casinos for which these drops are an insignificant loss, so I think there is no point in cheating, and to get the drops need a good turnover - which is profitable for the casino, so if the casino says 2.500 activation, then so it is - why he trifle

I think OP was probably referring to the airdrops that are done without any turnover or wagering requirements but just to random gamblers, and that is exactly the reason why he said how a gambler would know if the casino is actually transparent about airdropping rewards to the exact same amount as mentioned or they just do it to some and don't give away all the rewards.
But you are actually right that casinos surely get what they need back from such promotions since mostly more gamblers join the platform and even do deposits only to become eligible users of the platform to get a chance for the airdrop.