At Betflexi.com, we don't ask for that as we believe that player's privacy supersedes every other consideration. Asking for source of wealth is never a sure way to curb money laundering. There are far better and more sophisticated ways.
Are you among the devs team when using the word "we" signifies that you are also among the casino operator, however, I wouldn't want to capitalize your statement but it's deem necessary for a casino and gambling site to asked about additional verification or source of wealth if they the money isn't coming from the right source, this is to fight against anti money laundering.