I've read a lot of useful articles about collaboration with git. Many do's and don'ts, etc. For example, Top ten pull request review mistakes and a nice article about git workflow The Perfect Code Review Process, which is a nice way of doing it. Quite similar to the famous A successful Git branching model. I also really like this one specifically about rules with git, or ethics if you wish The 11 Rules of GitLab Flow.
But what I don't understand is why barely any articles ever mention what I find to be the most important rule of them all. To always make sure your main branch (usually master), is still fully functioning. The worst thing I know is when I am working on my feature branch, I merge in master only to realize my branch stopped worked. Or to have developers being stalled from starting on a new feature because the master isn't functioning as it should. In my eyes, tests combined with code-reviewing should cover this. But I rarely see articles mentioning this specific rule.
So am I wrong, is keeping the master branch intact not so crucial for team development as I think? Did the authors of those articles forget to mention it?