Maintenance access problems are cheap to fix in early design and very expensive to fix after fabrication, but they are often missed because the people who will maintain the equipment do not see the design until late. A 3D view of the concept, even without full engineering detail, lets maintenance and operations teams check whether there is space to pull a pump, lift a motor or reach a valve.
The key is getting that view in front of the right people early and making it easy for them to mark problems on the model itself. Catching a clearance issue at concept stage costs a design change, while catching it in the yard can cost a lot more.