In addition to security concerns the costs of a nuclear powered Cruise ship would likely be prohibitive vs a traditionally powered ship if those costs are anything like an aircraft carrier.
As per https://www.globalsecurity.org/military/library/report/gao/nsiad98001/c3.htm#:~:text=We estimate a nuclear carrier's,needed for the conventional carrier.
"A nuclear-powered carrier costs about $8.1 billion, or about 58 percent, more than a conventionally powered carrier to acquire, operate and support for 50 years, and then to inactivate.
The investment cost for a nuclear-powered carrier is more than $6.4 billion, which we estimate is more than double that for a conventionally powered carrier.
Annually, the costs to operate and support a nuclear carrier are almost 34 percent higher than those to operate and support a conventional carrier.
In addition, it will cost the Navy considerably more to inactivate and dispose of a nuclear carrier (CVN) than a conventional carrier (CV) primarily because the extensive work necessary to remove spent nuclear fuel from the reactor plant and remove and dispose of the radiologically contaminated reactor plant and other system components."
Cruise ship building and operating are commercial ventures. In the end it always boils down to economics.