That's just not how it works. The effect is cumulative. Imagine that 5% of particles could escape a mask. Then, one mask reduces the number of infected particles by 95% (hence the N95 designation). A second mask would further reduce incoming particles by 95%, allowing only 0.25% of the initial viral load through.
All of that said, we take our masks off to eat and that's probably the most dangerous time to be without a mask, so... eh? I guess I wouldn't care much if they dropped the mask requirement. But the CDC will care if a ship drops below Highly Vaccinated status.
I wasn't necessarily implying that just a portion of people wearing masks is as safe as everyone. Obviously that's not the case. But, and just my very humble opinion, I don't feel that mask requirements do a whole lot. Note, that's not to say that masks themselves don't do a lot (though obviously the type of mask you're wearing makes a HUGE difference (hence the CDC no longer recommended cloth masks) as does how you're wearing it (I mean how many people do you see with it below their nose!), but that mask requirements don't. Like you said, the restaurant one is the most obvious example. If you're taking them off to eat/drink, so probably 95% of the time you're in the restaurant, then really what's the point of wearing it for the 5% of time you're not at your table? If you're indoors but you're passing someone in a hallway not wearing a mask, you're only in close contact with them for a few seconds, so pretty unlikely to be exposed if they were positive. And if you're eating or drinking indoors you don't have to wear it anyways!
I mean, right now at my work, I have my own office so when I'm in it alone I don't have to wear a mask. But, to go to the bathroom which is like 25 feet away, I have to put on a mask. My staff, who are in cubicles, have to wear masks all day at their desks, even if there is no one in the cubes around them. So guess Covid can float over cubicle walls but can't go out my office door? hahaha
Again, I don't think the masks don't make a difference, I just think that mask requirements, particularly in places like cruises are, at the end of the day, little more than a CYA liability thing and aren't super effective to begin with, esp given all the other requirements cruises already have (vaccine, testing, etc.).
