Probably because food is a necessity.
I’ve resigned myself to the eventuality that I will be exposed to omicron in sufficient doses to cause infection, and that my vaccine and booster may or may not be enough to prevent infection entirely. I am very confident that the combination of my vaccine status and overall health will make it bearable; if I were older/sicker, I would be getting my groceries delivered. But no one is going to keep me from returning home from the grocery store with an active infection; I can’t say the same for international travel.
So people are stupid - apparently moreso in some places than others. If you were terribly concerned, you could make an effort to shop during off hours, or have your food delivered.
It has been an exhausting process that each of us has had to decide which activities we previously considered normal and routine now constitute irresponsible behavior or excessive risks.
Make your own decisions. The same way you disagree with the maskless people breathing on you and your produce, many of us would choose other than to go on a cruise. Hell - doesn’t bother me as I’m masked and have no plans to cruise or visit AZ. In one respect, the possibility of offing unvaxxed assholes could be viewed as a benefit! 
I’m booked on one next week. I don’t actually know for certain yet if I will be going , since I can cancel up until the " morning of" but
- The cruise line I am taking requires everyone to be vaccinated. No exceptions, not even for children too young to be vaccinated. They also test everyone right before boarding.
- I recently had covid and recovered. ( a potential reason I might cancel is if I still test positive a couple of days before)
- I cruised in October, before Omicron. That ship was at approximately half-capacity and there really were not the kind of crowds I am accustomed to seeing on cruise ships. The current sailing of the ship I am booked on is at approximately 25-30% of capacity. Next week may be higher, but I doubt it will get to 50% .
- Masks will be required in indoor public areas except when eating or drinking. I will not be spending all that much time indoors.
- This is probably a big one - my husband and I don’t have jobs that lend themselves to working remotely long-term. My husband worked from home for about a month at the beginning and I have worked in-person every day that I have worked. I might feel differently about going if I had a job where I had been working from home and getting groceries delivered for the past 2 years.
If any of those items had been different, I might have cancelled.
I am fully aware that ports and entertainment may be cancelled- but I also know that was a possibility on any cruise, including pre-Covid. I realize it is possible that I could end up isolated ( although I don’t think it is likely) and I can live with that possibility - I don’t think being isolated on a cruise ship would be that much worse than being isolated at home.
ETA - I live within driving distance of the port- if I had to fly, I’m pretty sure I would have cancelled.
No cruises for me for a while.
We cancelled our St Martin trip but have kept in touch with friends who went. One woman we know was unable to get a test (there were none) so she could not enter the airport.
When she secured a test several days after her flight she tested positive, so once again she could not enter the airport. But she had paid a daily insurance policy required by the island to cover eventualities such as this. She thought she’d be staying in her apartment, but no. She was taken to a tiny room with a bed that was pretty close to squalor. She was not allowed to leave the room! Think prison. Meals-on-wheels brought her breakfast, lunch, and dinner. She couldn’t cook in her room. The day she was supposed to be tested for exit, there were no tests. Eventually she tested negative and was allowed to leave.
I love cruises. I’ve been on quite a few and enjoyed myself greatly. Nevertheless I wouldn’t go on one right now.
But really, it’s a matter for you to decide yourself. You have to decide how careful you want to be vs. how much you want to partake of the risky activity.
For example, as I said I wouldn’t do a cruise. But I have flown in airplanes a lot recently. (US domestic flights only, so no issue with crossing borders.) I eat indoors in restaurants all the time. I’ve even gone to a few live concerts, including one mega event with 60,000 people.
Because those are things I really want to do, and for me they’re worth the risk. (Needless to say, I’m fully vaxxed and boosted, and I wear a mask.)
I’m aware that could happen if I wanted to fly back from another country ( or maybe even from another city in the US - IDK) which is why I said I’m pretty sure I would cancel if I had to fly to the cruise. But I don’t have to fly - worst case scenario as far as isolation goes is I have to stay in the room for the remainder of the cruise.
You couldn’t pay me enough to set foot on one of those things even if there was no such thing as disease.
Not a chance in hell. I know way too many people who have gotten omicron in the past few weeks after their booster to convince myself that everyone being vaxxed and boosted means I’m unlikely to pick it up on a cruise ship. It’s not covid og. It’s not even delta.
We did an 8-day in October and a 4-day in December. It’s a lot safer than going to the grocery, frankly…
We’ve got a Danube Viking cruise booked the end of March, and I’m very dubious about going. We have good travel insurance. We’re waiting to see what happens when the season begins.
We booked before Omicron, when things seemed safer. However we did make it from here to Indianapolis in multiple airports on multiple flights over Christmas with no problems.
I wouldn’t think twice if the opportunity came up, I’d be on the ship like a flash.
And I’m Covid high risk, old, fat and in recovery from cancer treatment.
There were major disease outbreaks on cruise ships before COVID; I don’t hold out a lot of hope that they’re going to make it through the current crisis without more major outbreaks.
Reading the news recently about Omicron sweeping through cruise ships, I would not go. Passengers shut into their staterooms and really subpar food provided.
I have a cruise booked at the end of the year. I’d like to go. If we don’t get another wave of something like Omicron we probably will. This is just a terrible time to try it.
What about the possibility of infecting others if you get Covid? It is not only your decision, it is a decision you are making for everyone else you come in contact with.
To paraphrase my increasingly demented MIL when we told her she could kill someone if she kept driving, “Well, that’s the risk those other people take!” 
I wouldn’t do it but I’m not even going to the grocery store right now. I’m really avoiding the risk.
But honestly I can see the appeal, if you’re a serial cruiser. Especially if the boat will have 50% fewer passengers. I love going to baseball games and I really loved going to games when they only allowed 20% capacity.
As long as you’re prepared to be infected, and prepared to quarantine away from others for a bit on your return, then you do you. Have fun!
Washington Post shared this about cruising right now
That article has a link to the CDC’s cruise ship tracking site. That sure is a whole lot of yellow for the last week.