without a doubt because many people abused the faucet..made many bets just from the faucet with high multiplier..once they won, they withdrew it...claim the faucet again, bet on high multiplier and withdraw...this will always happen in any sites which gives huge amount on faucet.
of course this is not a good situation for the site...

P.S 500 satoshi is a standard amount on dice site, even some site gives less than 500satoshi. And as what OP said, there will be a leveling system on the faucet, means that the higher your level the higher the amount you get from the faucet.