according to this, their withdrawal fee is $3.11 which is almost the same as the subtracted amount from your withdrawal. you can click the link on the quoted post if you want to see the whole thread.
Stake | | | 0.0005 BTC:  | | | 0.00007 BTC:  | | | ETH, LTC, DOGE, BCH, XRP, TRX, EOS | | |
It is a big amount to go missing especially when some Sportsbooks don't charge anything.
it is one of their ways of earning money. if you think the amount is too much, better use a gambling site that don't charge anything when withdrawing.
Exchange and casinos use this as a way to earn money so they can sustain their operations they cannot rely on gamblers' losses they have to make extra revenue and additional charges and trading is one way to cover the cost, especially from a casino that's spending a lot of money for their ambassadors and marketing, there are casinos that's not charging a withdrawal fee but you will have to trust them that they will keep their promises I prefer a small amount of extra in my withdrawal as long as the casino is reputable.