Not sure there's much to explain. Using integers for math in digital circuits is far more resource and computationally efficient than floating-point math. It has been decades since I did the math on the difference. I'll just guess that it could easily be an order of magnitude better across both metrics.

At basic level it is very simple: A 10 bit bus gives you the ability to represent numbers between 0 and 1 with a resolution of approximately 0.001. 12 bits would be four times better. Integer circuits can do the math in one clock cycle. Hardware multipliers do the same. To rescale the numbers after multiplication you just take the N high bits, where N is your bus width; which is a zero clock-cycle operation. Etc.

In training a neural network, the back propagation math can be implemented using almost the same logic used for a polyphase FIR filter.