I think once the business gets larger than a few thousand people there's just no way to completely avoid the money and effort wasted making various systems work together.
You have groups that do things *this way and have *these vendors that provide data in *this format while some other groups do things entirely differently yet have to process and integrate the data from those other groups. The output changes based on political whims of the department heads or who can negotiate a better contract with who.
The efforts to clean up and consolidate never stop nor do the jobs for people who make it happen.
I've been involved in projects that successfully clean up and consolidate some particular area but it's never *everything and there's always another one around the corner.