Many changelogs not showing

In The Hub, open site, go to Plugins, select a single plugin, then click Changelog. Many of the plugins do not offer a changelog. But even when the data is missing from the Hub, it is present in the page for the plugin at

Where exactly is this data sourced from, and what can we do to help ensure that we can see the changelogs here - like, ask developers to post their logs in some specific way? At this point I don't know if Dev isn't sourcing data properly or if other developers aren't doing everything they need to do. Thanks.