The "problem" with SK passenger ships is the lack of exclusivity. When first discussed, passenger cabins were only supposed to be able to be installed in passenger ships; regular ships couldn't take anything above refugee/prisoner-class cabins. So if you wanted to run rich passengers that actually paid you decent money, you pretty much needed to buy a passenger ship.
It seems to me that they were worried nobody would do passengers if they were forced to by a special ship just for passengers, so they opened it up almost all the way, so that only Luxury-class cabins were exclusive to the passenger ships. But given that Luxury passenger missions are few in number and hard to find, that particular niche seems to have been squeezed out of existence.
I think they could restrict things a little more, perhaps by ship class. Cargo transports should be prisoner-class only. Multiroles like the Asp and Cobra, maybe up to Economy. The Anaconda's got that "ten-forward" observation deck that just screams business/tourist class. Sleeker-looking ships like the Clipper could go up to First, while the top classes were SK only. Stuffing a T9 full of high-class passenger cabins is as silly as trying to fill an oil tanker full of holidaymakers.