We don't need to. All withdrawals are processed manually
Plus the system wouldn't allow it to complete if there is not enough balance. Also in some cases it is useful.
Also you should complete your Rollover that came with the bonus before requesting payouts.
Where do I find the rollover? Is there an statement in my account that says I need to put in X amount before I can withdraw?
That updates every time I play a given game? So I can know how much more I need to play before I can withdraw?
If there isn't, I am playing blindly without ever knowing when I can withdraw.
So all I can do is play for hours, attempt withdraw, play more, attempt again?
Unless I am missing something, or its somewhere in my account.