This was how this idea came about, thinking if casinos will make such a feature available like it is with trading where a trader can set a take-profit at a target price, and once the market price reaches that level, the take-profit is executed even if the trader is not online at the time - casinos can introduce a similar feature with cashout where the gambler willing to accept a cashout offer can set/tell the system to automatically accept a cashout offer of 2x, 3x, 4x 5x up to 10x or more when ever it's available, and depending on the cashout X-amount the gambler chooses, once such x-amount is available as a cashout offer, the system will automatically execute it for gambler whether he is online or not.
I now understand what you mean, but there's no casino or sportsbook that have allowed this settings, I believed its because they don't want players to always be at the advantage of taking cash outs all the times.
Just as you were not available online, to take the cash out, that's how so many players lose the opportunity to take cash outs and if casinos implement that new feature that you have described, they know it will be a big opportunity for gambler, that's why they might not allow it. It's just what I think.