Heres the problem---lets say you train chest once a week for a year and you hypothetically gain 1/64 of an inch in pectoral thickness from each workout. At the end of the year you should be at 52/64 ( or 13/16 ). Almost an inch of thickness (pretty good).
To build muscle we are trying to lift at a high enough intensity and load to grow muscle but with enough recovery so the muscle remodels and grows. The problem is everyone is loading up on the volume end of training and its taking away from the recovery part of it.
You can train in a way so you can train chest 3 times every nine days and you will recover and grow faster than ever. If you train chest 3 times in 9 days you are now doing chest roughly 136 times a year! So instead of 52 growth phases you are now getting 136 growth phases a year. I personally would rather grow 136 times a year than 52. At a hypothetical 1/64th of an inch per workout you are now at 136/64 (or roughly 2.1 inches of thickness). So now your growing at roughly 2 and a half times as fast as normal people who are doing modern day workouts are.