To be honest, my experience of private enterprise is that they insist on doing things hard, slow and very custom. Almost every problem that exists is distinct enough that you can argue it doesn't fit the existing COTS software. It's sometimes necesary to build something yourself, but no where near as often as it is done.
If I remember correctly, John Ralston Saul made the point [0] that there is little observed difference in terms of the efficiency of decision making between large government and large corporations.
My personal experience is that large organisations and government are barely distinguishable. This is often excused in the name of "risk mitigation" - but in my experience it's really just that there are more snouts in the money trough, and that politics is more important than success. The close ties between government and the largest organisations also invite a similar culture.
The end result for both government and large enterprise is "hard, slow and very custom". (Of course, there are exceptions in both government and enterprise).
Some might do it under the belief that it makes them more flexible later on, but going with off the shelf stuff means it's easier to find people to create and migrate to a custom system when or if it's needed.
