You have rightly pointed out a crucial issue here.
However,as you also know Security is usually an after-thought in such Systems.
Why is that the case?
In their rush to satisfy consumers they neglect basic security best practices till its too late.
"They want as few roadblocks to customers Internet using experience as possible".
Do read the last line of the Blog which refers to this issue only-
The customers' enthusiasm for on-board connectivity led Royal Caribbean to alter its business model. It used to charge a premium for few people to use the Internet; now, it charges little to connect as many people as possible. "It was a major point of guest satisfaction," Martin concluded.