As a non-Japanese couple in our late 30s who decided not to have kids, I confirm those are exactly our reasons.
While I generally love kids and will be a good uncle, I just can't fathom the financial/emotional/time burden required to raise a couple of them for 18 years. I have just one life and this is my ride. If regret will eventually show up, I'll deal with it.
We're in our late 30s and are definitely not having any.
That said, I believe that a couple that is 1000% sure they want to have children and know what they are getting into should absolutely do it. The issue is that there are so many parents/future parents locked into the "you'll never be ready" or "you can never be too sure" mentality and fail to fully grasp what you're sacrificing and leaving behind when you become a parent.
I fear for people who choose this path. Being childless in your 30s sounds like a blast. But that's just one stage of your life. How fun is life going to be when you're 40+? Or when your health begins to decline? Maybe it will be worth it, maybe not. When I visit older relatives who are childless (at least to me) their lives come off as hollow and sad.
My grandfather willingly moved to Florida, away from the family. We'd be expected to visit for holidays, of course, but he wanted to play tennis in the sun.
Having children is also an opportunity for personal development and growth, just of a different flavor and different direction.
Of course there isnt a single answer, but I think people should question the implicit assumption that the "best ride", most fun, ect is the childfree one.