1. Gov thinks it needs some simple form building 2. Chooses a vendor form building framework, some mashup of ASP.NET usually with workflow tools 3. Oh, we'd like documents stored, and an integration with another system, and a custom reporting tool, and a payment function, and a appointment booking. 4. Vendor doesn't want to lose business so builds custom code into the "simple" form/workflow tool.
All of sudden the simple form tool is customized beyond belief, falls behind on updates and becomes impossible to change. Worst still, nobody wants to invest in it because it just-about-works.