No one who knows the procurement process thinks it is easy to change. That's why legislative and regulatory changes sometimes have unintended consequences or bizarre beginnings. For example, the requirement for certified cost data came about because of a concern that defense contractors were sandbagging targets in incentive contracts. This small issue sprouted into a major program. Also, it doesn't help that training budgets haven't kept pace with accelerating change.
Some people cling to old ways they know instead of using new ones for which they are unprepared.
The boldest innovations are in commercial-item procurement. But too often solicitations for commercial items contain the familiar old Federal Acquisition Regulation clauses. Agencies even fail to use the FAR's abbreviated clauses for commercial items, falling back on the more extensive traditional ones. Prime contractors compound the problem by flowing down unneeded clauses in contracts for commercial items. One reason contracting officers do that could be that they are uncertain about what commercial clauses should replace the FAR ones.