Isn't it that you biggest winning is confidential? It should be kept in private because people are really sensitive nowadays. There are people who are judgmental enough to judge you, when they know that you are a gambler. But on the other hand, your winnings will reflect on how you gamble effectively, most especially that gambling is really risky.
While I agree it should be kept private the gamblers might not have a choice because I remember there are casinos with certain terms about having the rights to announce the winnings of their players as a way to advertise the casino.
I can recall a few good wins from different bitcoin casinos but all of them are nowhere near the million level. And this is probably because most bitcoin casinos limit the profits per bet to avoid the risk of damaging the bankroll.