Not all sites need/want commenting. Implementing this as a plugin allows complete removal of commenting without having to add more code (such as the Disable Comments plugin).
If it's a plugin, it can be added back when needed.
There already is a petition that proposes to move commenting under Posts instead, see here.
I'm not sure that removing it and moving it into a plugin is an idea that will receive a lot of support as there will be a lot of work needed to get that going.
Also keep in mind that the commenting system is used for example for WooCommerce product reviews.
And if one were to continue that line of thought, then Posts is also something that can be moved to a plugin, because not every site needs blog functionality.
It won't take long and the whole of ClassicPress becomes an empty shell with plugins adding all functionality ;)
As said, comments are not always user comments. They are data structures attached to posts.
better add a way to disable them globally without use a plugin or a filter
Maybe just have an easier way to bulk disable it, even for older posts.
> As said, comments are not always user comments. They are data structures attached to posts.
Yes, there are too many potential conflicts with converting comments into a plugin even if its bundled as a Core plugin. For better or worse, it is one of the nuances of the WordPress world and post meta data...
But certainly making it easier to hide or disable is a possibility.