Maybe a helpful metaphor is that the “stable” branch is like the disc based Microsoft Office, whereas the “tests-passed” branch is like the cloud based Office 365. Both are viable options, and both get updates eventually, but for a product that’s fundamentally online already and which has a small support team, it’s more productive to be able to instruct people to update their installations to the current code, so that bugs can be tested and fixed promptly. As a forum admin it’s great to be able to report a bug and update to a version that fixes it within a few days, sometimes even the next day. I haven’t used any other web apps that are as responsive as that. (Not that every bug is fixed instantly, but many are.)