Putting software in production can be a challenge, often the frequency of going to production is low and the amount of changes/features involved is high. This usually results in a long and painfull deployment process. The release probably contains as many changes as possible because if you do not get your change/feature in this release the next release may very well be in 6 – 12 months.
To create the illusion of being able to prevent this and have more control the deployment department is often confronted with huge, 100+ pages, deployment guides decribing the deployment process in numerous, usual manual, steps. Incidents occur in the newly deployed software. Since there were so many changes in the new release, how are we going to find out which part of the newly deployed software is causing the problem.