Change is the enemy of automation
So you've got a bunch of screen-based processes and procedures you have to carry out: Whether it's adding new users, updating the helpdesk status of support requests or reporting the consumption of storage space across the enterprise. All fine and dandy, then some numpty in another part of the organisation goes and changes something.
They might do a software upgrade to the storage manager, or patch the helpdesk software or change the default width of the user's address field. Whatever it is, no matter how far ahead they published the change notice or how innocuous it seemed at the time, things like this break automated processes. You can't test for them before deploying your automated scripts as the nature of the change is unknowable (even down to correcting a spilling mistake that you were screen-scraping for, or creating a new one that you now miss). Hence you now have to spend the time you saved automating something to fix the automation script to account for the new environment.
The end result is that as long as people make software changes, we will always be playing catchup with our automation suites. So all that happens is sysadmins go from spending boring days doing repetitive tasks to boring days debugging faulty automation scripts.