So - liability.
On top of the liability that a firm can run into if it doesn't get drawings issued on time (a lot of Revit cheerleaders also don't know anything about contracts - and what happens if you do not fulfill them), there is also the liability that an architect or engineer takes on when they issue construction documents.
As a designer, I do not immediately take on this liability - however my boss does, and if he gets it square in the nuts because of a mistake I make (though he is responsible for reviewing everything I do) then even if I was going balls deep on the Revit cock I wouldn't be here much longer. Everybody makes mistakes, but all it takes is one major one that leaves either he or the firm exposed to liability, and it's 'GTFO' time.
Most of these major things don't come up until the building is under construction - or indeed, until after it is built. Once (hopefully) clear, easy to understand, and hard to misinterpret construction documents get issued, then they are immediately torn a new asshole by all of the people involved in the next stage of the project. They are subject to approval by Fire Marshall's (Local, State, Federal - depending on project), Electrical Inspectors (same), and other Authorities Having Jurisdiction or 'AHJ' that are specific to the project - like the FAA for example (for projects in or around airports), local utilities, telephone/cable, etc., etc., and of course - the contractors (who will get their own post soon) bidding the job.
I have always found it amazing that the Fire Marshall's offices can review and review, make comments, request corrections/alterations to designs, but then when they show up in the field, it's like you are dealing with a completely different organization. Often it's not the same guy who reviewed it - and despite being fairly good at their jobs - I have run into at least one problem where a NICET 4 certified Fire Marshall inspector was making erroneous claims (that my NICET 5 certified fire alarm installer buddy slapped down). They usually get whatever they want, but not that time.
At any rate - a Fire Marshall can come into a completed building, point and demand tens of thousands of dollars worth of equipment be installed, and withhold the clients certificate of occupancy. Guess who they are going to blame? The Fire Marshall? No. The contractor? No. It's coming directly back into the lap of the engineer (and/or the firm he is partnered with). The same goes for any other AHJ, and if schedules get screwed up because of it - then it's going to get ugly.