Why are hashtags so important here?

The short version is that there is no algorithm. The long version is that hashtags help you to both find the content you like, and filter out the content you'd prefer to avoid.

Using hashtags takes some getting used to. On Twitter, they're used by trolls to mob people over disagreements. There are no trolls here, so hashtags are more of a necessary way to keep things organized. #CoSoTips