Not too long ago, factories were places were full of people with only one thing to do and not a lot of decision making about these tasks. The jobs wore out the worker, it was not just mind-numbing, but also intellectually draining. Machines were used in the process but only to carry, weld, screw or paint. A factory worker needed only to do one thing, and kept on doing that same thing every minute of everyday, day in and day out.
At some point, the factory would have hit a wall in terms of production volume, as a person can only do so much in one day. The only answer was to have more repetitive processes automated using programmable machines and robots.
The modern manufacturing automation systems used in high volume and high technology precision factories around the world enable a level of production which ensures high quality across the board. Machines are better at repetitive tasks, and programmable automated systems allow for better fine tuning of the process. This feedback loop makes for better quality control and quality assurance for the company. When the time comes to change the assembly line with upgrades or a change in products, the automated systems also allows for a faster turn around time.