If you have cool software, you definitely want to make it better and better and work on new releases. Each time you release a new feature, you need to communicate it to your users in a comprehensive manner.
Release notes are also dry facts, rather short, and must highlight implications for the end-users. They must catch attention but remain professional and deliver substantial information.
It is a new emerging writing genre that I like a lot. Release notes are a new breed made of press releases and online tutorials. I have worked in a company using Salesforce Einstein Analytics and often communicated recent EA updates to my colleagues. My task was to scan all release notes (a thousand pages sometimes), select only necessary information, and make it even shorter, but emphasize how it fits with our use cases.