Daniel, I think the perspective here obviously changes depending on the kind and nature of the drawings that are typically done. In my field, contract or design drawings are seldom of use in preparation of shop drawings. The only time I've requested CAD files from consultants was to create site plans in our shop drawings- which are included "for information only". But in those cases, the consultants didn't make a big deal out of it, it was just a matter of getting hold of the right draftsman to email the file over. I didn't have to sign any waiver, just explained what I needed the thing for.
I can see how in the layout of a sprinkler system, it would be very convenient to have CAD drawings that had all the structural/ electrical, etc., laid out on them- everything that you either attached to or had to dodge around. If those drawings existed (and assuming they were reasonably complete, coherent, correct, to scale, etc.), then that would bring about the set of circumstances that has been discussed above.
It seems to me that the trend is toward this idea of shared drawings, rather than away from it. At least the CAD companies seem proud of their products that enable a foreman on the jobsite to pull up a detail from a structural drawing. They do have CAD viewers specifically for this purpose.
Here in the last few years, I have worked on a number of bids where all the documentation was given in electronic form. In some cases, it is CAD drawings directly, in other cases, .pdf files. The most recent such case was for the US Navy.
You asked the question, "If I pay a draftsman to produce shop drawings, why should I give them away?" The catch in this case is that the consulting engineer has already been paid by the owner to produce those drawings. Certainly the consultant can pocket more money by charging whatever the market will bear. But is that action in the best interests of the client?
A similar circumstance comes up in the furnishing of soils reports, or working documents for construction. Why not charge the contractor hundreds or thousands of dollars for these, as well? The usual practice is to furnish these items free, or at the cost of reproduction. I think most owners would recognize that whatever overcharges they were to put on those items would simply get added to their project costs in the future.
Let's change the circumstances a bit for comparison. Suppose you are the contractor on a job, you draw up your shop drawings, and hand them over to the consultant. He then tells you, "It will cost you $5,000 for me to review your shop drawings." What's wrong with the picture? The consultant makes money on the deal, plus the owner also pays him to review the same shop drawings. The contractor has already bid and is stuck with his bid, so it doesn't cost the owner anything extra. Yet, it's obvious that there is a problem, and the net result would simply be to drive prices up for any other future clients of that engineer.