Isn't the real reason for this rule to avoid arguments after you tell your opponent they just lost the game? By saying "you're on two" and getting a head nod, you've had the discussion and avoided the argument if they lose on 3 fouls.
Why does it matter WHEN you tell them? As long as it's sometime between the 2nd foul and when they lose the game due to 3 consecutive, isn't that all that matters?
Seems really NIT-picky.
The reason is not only to avoid arguments but also to ensure that your opponent is fully aware that he needs to make a good hit or the game is going to end.
Sure it sounds a little nit-picky if you are simply warning them, shooting and they are at the table within a few seconds. But what happens if things play out a little different?
For example, let's say I commit my second foul and immediately my opponent warns me that I am on two. Then my opponent who happens to be an extremely slow player stares at the table for 5 minutes deciding on whether or not to go for the run out. He then tries for the run out. He plays really slow and gets all the way down to the end where he hooks himself (5 more minutes). Then he is hooked so he takes another 5 minutes to plan out his low percentage multi rail kick shot. He finally executes a good hit but no more balls are pocketed. He then sits down and I approach the table.
It has now been 15 minutes since I was last warned that I am on 2. Regardless of whose fault it is, I have forgotten that I am on two. So now I shoot at a ball and accidentally scratch. The game does not end because I was not aware at the time I played my shot that I was on two.
So the rule is meant to avoid arguments and also raise awareness. It's important for the shooter to be fully aware of his situation before shooting.
And if you compare the same logic to straight pool, you can be sitting down for an hour between innings so it's very easy to get distracted and forget that you are on two.
I can't believe how many people on here are disputing the rule as if it's a controversy or something. This rule is set it stone. There is no grey area. Either abide by the rules or don't and leave yourself open to the consequences. Obviously if you are gambling you can use whatever rules you prefer but unless you decide on a rule change ahead of time you better be prepared to follow the standardized rules.
When I first posted this I figured everyone would have just agreed and said that it's common knowledge but now I'm glad that I posted it because a lot of people on here are misinformed. Wise up people!