Daily habit tracking is something useful, but can clutter up a calendar view. Also, not every day is each habit necessarily completed, for example if the target is 5 workouts per week, then missing two days per week is not terrible, but expected. Therefore it can be useful to have a separate widget that helps provide the overview of habits and to quickly check off the habit completion.
As of early 2021, Notion does not have recurring tasks. There are several workarounds for this, with various tradeoffs. Which approach to use has to do most with what kind of recurring tasks are being supported: daily habits, weekly or monthly tasks, ongoing tasks such as shopping lists, etc.