We do have a few clients with reef tanks but there are some practical reasons to why its not popular. The biggest factor being cost, cost of the corals themselves, additional equipment, and the time and effort it takes to keep them happy. For most saltwater clients we bring pre mixed saltwater in buckets to do the water change. Well on a reef tank its preferred that the client have a mixing station in their home/ business so we can mix to the exact ideal salinity for their tank. This also means the added cost of a RODI unit and upgraded lighting has to be factored in to the clients costs. then when you break the news that the pretty trigger, puffer or in some cases angels are not reef safe it simplifies the decision. Add on the fact that most clients are not hobbyists and cant tell the difference between live coral and the fake stuff it just makes sense.
Planted tanks are much more common on our client list (probably because I push them so often) but regionally our water is hard with a high PH (7.8- 8.3) meaning the African cichlid is king, so no aquascapes here. For the most part clients want big colorful fish and a tank that looks full, with as little input from them as possible.
The most difficult part about my job is constantly reminding myself that 99% of my clients are not big hobbyists and just want their customers to have something pretty to look at. Unfortunately most cant tell an mbuna from a peacock or a tang from a wrasse.