People don't appear to be divesting from the bankroll. 
The lack of divestments could also be because we're not at a profit all time high, and commission isn't charged until then. Current investor profit is 6150BTC and ATH is 6167.8BTC, so there won't be any commission charged until players lose another 18BTC. Would be an additional 0.5% profit based off of current bankroll size.
So, "someone" has to divest to make the profits bigger, but nobody wants to be that person. It's a good problem to have honestly, think about a casino that has so many people trusting it with their money that the bankroll exceeds what it should be, that's a good problem to have.
There are so many people who would have hard time finding 1 bitcoin to bankroll their casinos, I could start a casino tomorrow and work for a whole year and I wouldn't even get 10 bitcoins invested into mine, so even though this drops the amount of money people could make, it's at least something that doesn't disturb the system.