That is a very good question and one of the reason why people use a 15 pound bowling ball is due to the weight and it’s not too heavy and it’s heavy enough to knock down pins. I have used a 14 pound bowling ball is not bad at all but it does tend to be a bit lighter to use and you may throw the ball much faster due to the weight and the weight is one of the reason why people gets more pin action.
See the lighter the bowling ball, the less pin action you will have. You can only throw a bowling ball but so far hard and so far and the harder you throw the bowling ball, the less control that you have. On the other end of that, a 16 pond bowling ball is heavy and you really can’t throw but so hard and fast. Yes a 16 pound ball hits the pocket different and harder and which will help with pin action but the ball is heavy.
You are not a machine and over time throwing that 16 pound bowling ball will take it’s toll on you. This is why the 15 pound bowling ball is the sweet spot. It’s not light and it’s not super heavy to use and with a 15 pound bowling ball, you can throw the ball hard and fast or slow it will still have some good pin action.
Sometimes it has something to do with the oil on the floor, with heavier oil on the floor, a heavier bowling ball may be needed to help cut through the oil. It really depends on what you want to do. I know a lot of older people who uses a 14 pound bowling ball cause it’s less stress on their body over time and they are just tired of using something heavy all the time. So if you have some back and arm problems, using a lighter bowling ball will help over time with less stress.