I think the only possible scenario.

He does not meet any withdrawn amount and wants to collect all funds from various crypto currencies into a single coin. Could be he got those amounts from Referral, Tips or Rain and wants to bet with at least a good amount of money or reach the minimum withdraw without making a bet.

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I'm doing those on (CHIPS) casino while, I receive my lock-token reward. Exchange all currency from vault reward into a single coin using exchange feature, so can easily bet with good amount money and more faster reached minimum withdraw.

I don't think the reason because the fee-withdraw, because the fee is small on those currency.