A lot of threads in gambling section are basically dedicated to scam accusations. They can be seen every day on the first page. The casinos about which people complain are usually new or known to be scamming people (one can easily check out the trust of members leading the respective ann threads to be assured in that). I don't understand why people deposit money onto new casinos and then complain that they scammed these people. I mean, there are lots of very trusted casinos offering a wide range of games, so why not to keep playing at them rather than some unknown risky ones?
Probably they thought the luck they could not get in winning from the first casino, they will be able to find that luck in the new one until they realize it is the same thing and then move to the other ones until they get frustrated. Like you said, there are so many trusted casinos, but even the trusted ones are out to still get most of what you are holding anyway, so what is the point eventually ?
The experienced one won't go hunting for lucky casinos, but for better house edge. In online Casinos, Luck does favor no doubt, but not completely. Better role is played by house edge which is set by the owners. Other than better winning chances, also psychological things does plays it parts, like better design, colors and all. Addiction is basically the primary point where this few factors acts as influential factors.