I just found it quite peculiar because even a dumpster fire like Kanojo no Tomodachi has comments:
If a series doesn't have comments on a japanese sit it's usually a good thing.
As the other poster commented, Japanese readers like to buy physical versions. A significant number these days also read digital, but the way they consume it they pretty much keep the same. They do not feel the need to express their opinion every single chapter, nor connect with other online readers, because it's frivolous and superficial for the average user. Unlike in the west where everyone has to have an opinion and discussion on every single piece of new info or media.
If they have good comments they want to share, they will do it on Twitter and speak more generally than on a chapter by chapter basis or only if something really significant happened. If they have constructive comments, they'll direct it to the author on Twitter or pixiv...because you know that's actually useful, unlike 99% of the "criticism" on this website that's just pissing into the ether.
And if they have negative comments they keep it to a select circle of friends, sometimes on Twitter, but usually on Line. If you're seeing negative comments a lot publicly then things are either really bad, or someone is trying to cancel the author or something. And that's when comments appear on websites that host manga. Only super low quality comments or malicious comments appear there if any, and normally it's none.