fightingthefuckits

I'm not OP but a huge benefit of BIM in general is being able to model a building in 3d way ahead of actual construction then use the model to coordinate key systems to ensure they work together. An example would be having the HVAC subcontractor model their ductwork, equipment etc in Revit, same with electrical, plumbing, structure, sprinkler etc. When you bring all the models together in the same space you can run a clash detection that looks for where these systems are in conflict, an example would be say a piece of ductwork running through a steel beam. Doing this way out ahead means you can be more accurate in ordering and fabricating material, less time lost due to finding these clashes in the field and having to rip out existing work to come up with a fix, not staying this no longer happens but hopefully it's less common. The sustainability benefit in my opinion is really in the form of reduced waste through better up front planning.

I think it may depend on where you are and what you're of work you're doing. In my area it's pretty much a pre-requisite for certain trades. I worked for a large general contractor doing things like large office buildings 250k sqft+, large residential, industrial etc. We required our major trades (electrical, hvac, plumbing etc.) to use BIM for coordination and clash detection. It was a little slow to adopt at first but gained steam quickly.