Why is tennis scoring system based on the numbers 15, 30, and 40?

The tennis scoring system is based on the numbers 15, 30, and 40 because it originated from a clock face. The numbers were used to represent points won in a game, with 15, 30, and 45 being easier to call out quickly during a match. Over time, the score of 45 was changed to 40 for easier communication.