On government projects, scope is constrained because it is not as open-ended at the beginning as in the private sector. In the public sector, scope is constrained by such considerations as who is in office, what the constituents want, existing legislation, an extensive set of rules for doing business and prior requirements, which typically must still largely be satisfied.
By contrast, it may be challenging in industry to develop requirements for an application that never existed before – but at least it is open-ended at the beginning. On government projects, I think it is a daunting challenge to define scope and develop requirements when you need to contend with all of these other distracting forces.
I am using the phrase “constrained scope” to describe a limited latitude to negotiate changes to the scope. In private industry, there would likely be a limited number of stakeholders with many common end objectives, but in government there are more often a larger number of stakeholders and the interests of these stakeholders tend to be divergent, since various departments tend to operate more autonomously, almost like separate companies. In addition, the ultimate stakeholder is, or should be, the citizens. Prior requirements, agreements and applications will severely constrain what can be included in a new system.