Excellent question! The scenario you described does work but the downside of it if that any component has public access to such variables and as a result can change the values, which can lead to unexpected side effects and code that is more difficult to maintain. A subscription from a subject prevents that and gives “read-only” access to that data. So that’s one benefit to the Subject approach. Another benefit is the ability to subscribe from Typescript code so you can react to new data outside of your templates.