Who decided that tennis scores should increase in increments of 15 - 40?

Answer 1

Interesting question. I looked up for it and Wikipedia says:

"The convention of numbering scores "15", "30" and "40" comes from quinze, trente and quarante, which to French ears makes a euphonious sequence, or from the quarters of a clock (15, 30, 45) with 45 simplified to 40."

Answer 2

Scoring in tennis was as stated by the previous answer except he omitted to add why zero is called as 'love'. This is because the '0' resembles and egg stood on it's end and the French word for egg is l'oeuf which soon became corrupted to 'love'.