In addition, commercial breweries have a chemist and a microbiologist on staff to make adjustments to the grain bill. Most likely thety monitor fermentation, and tweak temps up and down on a more active basis. In a commericial brewery, it isn't about quality its about consistency.
Exactly. It's also about sales volumes and recouping the cost of equipment as quickly as possible. If you can push the beer out of fermenter and into the bottles or kegs in 5 days instead of 15 days, your equipment is effectively 3 times less expensive, as it will pay off 3 times faster. In other words - it allows 3 times the output capacity for ~the same upfront equipment costs.
For home brewers like myself, with limited storage and limited consumption rate (I know, hard to believe!), brewing every two weeks for a year or so will produce a lot more beer than I can drink myself or give away to neighbors (about 100 pints a month).
The bottleneck for me personally is consumption/proper storage of beer I brew, as well as my own time brewing, experimenting with recipes, bottling etc.