The question of 2D and 3D graphics really comes down to the needs of the operators, and their experience. The facility operators that have been around for years likely don't need the "visually appealing" graphics, per say. Nice 2D graphics that give them the information that they want would typically suffice.
However, there is a shift in the industry where more and more operators are of a newer generation, where "visually appealing" graphics are expected. We are also finding that some operator interfaces are doubling as public-facing interfaces as well. A 2D schematic of a rooftop unit doesn't do John Q. Public much good, but if you show them a 3D representation of the "box" that they've seen on the roof, they can relate.
The argument for 3D graphics really comes down to the level of detail provided and the capabilities of the BAS. Many BAS still can't offer a 3D environment where the operator can zoom and pan in on a piece of equipment to get more or less point detail, diagnose system failures, or provide a visual remote diagnosis of the system. So, currently, we're stuck with providing a 3D representation of a system to provide a similar experience.
Cost is always important when evaluating any purchase but more and more 3D representations of HVAC systems are becoming available. Once a library is established, development of those 3D system graphics can be just as affordable as a 2D representation.
I do agree that the person driving the car doesn't need 3D graphics, but the mechanic could benefit (insert reference to Iron Man movie here). Building operators and managers don't just drive the building, they are also expected to maintain, diagnose, and prevent.