MY 50 CENTS ON DEVOPS TRANSFORMATION!
Manual deployments are tedious and repeated & yet require a great deal of expertise.
Asking experts to do tedious and repetitive, and yet technically demanding tasks is the surest way of ensuring human error that we can think of, short of sleep deprivation or intoxication.
Automating deployments frees your expensive, highly-skilled, overworked staff to work on higher-value activities.
Reference — Continuous Delivery by Martin Fowler