I've never done this, but if you read stories by people who have, they appreciate not having 3,000 other tourists on the boat; just a few dozen or so, plus the crew members who don't talk to you.
OP here - there were zero other passengers, and it was exactly the way you say.. the crew did not talk to me.. It was great! many long hours of ocean, days, nights, out in the far blue.. with no computers at all. When I arrived in Japan I was so rested! the passage into Tokyo Bay was so memorable! it takes time.. it was an antidote and clarity..