I think you're 100% correct that the company doesn't want to potentially upset their customers. Or more to the point they don't want them to dwell on the possibility that people can and do go missing while cruising.
But serious question: If that was your child or your sibling who went on the cruise and *poof* just disappeared never to be seen again, how would you feel about them not contacting the other passengers? Wouldn't you want them to do everything possible to find out what happened, or would you just shrug and say, "Do whatever's the best for your bottom line."
Edit -
Just to address the first paragraph of your comment:
I disagree that police can't or won't use email or other electronic communications to get the word out if the situation warrants it. It's not as if there's any law or official policy against using email, it's just that in most cases, they don't have the contact information of everyone who rubbed shoulder with the missing person. But on a cruise, they do.
In similar situations, the cops use Amber Alerts to notify a limited population about a missing child. And university police will send texts and emails to the college community when there's a security alert.
Also - the cruise lines don’t want to highlight the fact that their man overboard detection systems need improvement.
If a child had gone missing from the cruise, it would be national news. Here we have a missing adult, with 2 possible outcomes: he’s either alive or deceased.
If KM is alive, he most likely went missing voluntarily.
If he is deceased, it was an intentional jump, misadventure / accident, or he met with foul play.
While not impossible, we have no reason to believe he met with foul play. No word of an altercation, or even clarity as to who KM was last seen with. Apparently his brother saw him in the room, but he wasn’t at his side throughout the night.
The public will help when asked. As an example, Gabby Petito was located when a family searched their trip videos and saw her van. In Gabby‘s case, the most likely scenario was foul play and finding her body was critical to the case, which provided a reason for the public to want to assist.
In KM’s case, foul play is the least likely scenario. People who were onboard the cruise can look through their photos all they want, but unless they have a photo of KM going overboard, it won’t prove much. This isn’t a rescue mission, and it’s not even a recovery effort.
Sadly, the most likely scenario is that KM went overboard, and his body will not be recovered.
jmo