Although your suggestion is Wright, but sometimes our emotions plays a big role in our lives. If you can't control your emotion you can't control your time. Because when ever your emotion I'd working time has nothing to do. Although the time and emotion works together but I think it's your emotion that control the time because there will be a point in time when you loss more often and you choose to continue until you win without considering the time countdown and it will definitely affect you.
But putting a timer might help us than not putting at all. This is because when we see the timer, we can pause for a while and think if we are committed on changing our selves for the better. If yes, then we will decide to stop no matter how hard it is or even if the urge is still there. If time is not important, there won't also be clocks around that will be invented.
We all have our responsibilities in life but it was mostly our jobs that will let us stop doing unnecessary things because it is more important than them. Apart from the time and responsibilities, it was also the budget that gamblers are looking at before they decide to continue or not.