That's some 30 years ago. But I lied. I don't remember ever having Absinthe' come to think of it. I may have. My grandparents were European and had all kinds of exotic bottles I may have sampled. But Chartreuse? It was the only thing strong enough after awhile. (sad, I know)
It seems the reason for it lies in clock faces being used as a scoring system. It's a good example of a less than perfect solution, but it was a solution nonetheless. The tennis scoring system seems odd because we're used to more simplicity. But it's only strange if you disregard the daily lives of people in the 15th century. Most would be unfamiliar with the idea of 'visualisations' as we are, having very little to base them on. But everyone (or at least everyone who mattered) was familiar with the image of a clock face.
So it is a logical, primitive score board. Perfect. Except that the rules demand a game be won by 2 clear points. Which leaves the clock face score board 'short' by 5 minutes. Practical as ever, the esoterically inclined French, unwilling to abandon such a cool idea as a score board, knocked 5 minutes off and were able to make things fit. Hence, 15, 30, 40. If this is true, I wouldn't be surprised if it is also at least partly to blame for the 'advantage' system, which I think is there so people don't become even more confused.
More than welcome. :) I have a great deal of time for the French. A truly wonderful people with a unique way of seeing the world. They really don't care if it doesn't make sense, as long as it makes sense to them.