I would say that the biggest contributing factor was probably cost.
In bigger sizes like 4 inch, compression couplings can run as much as 3 times more expensive than set-screw couplings.
If the installation is indoors and has no need for weather-proofing, I can't say that I see a reason for compression couplings except asthetic value or ease of sucking a pull string through as was mentioned earlier.
If it's above the cieling or otherwise hidden, a wrap of "jap-wrap" at each end of the set-screw connector will greatly improve the runs jet-lining ability.
As for getting large compression couplings to tighten properly, the trick I've found is to use two strap or pipe wrenches that you think are completely too big for the job.
In regards to the grounding aspect, I've never had a problem with set-screw connectors as long as you make sure to tighten the screws all the way.
