To drive home the point of why FormGroups are useful, I'll show you how to conditionally hide/show a FormGroup based on the value of another FormControl in the form.
In this scenario, we'll add another FormControl that is a boolean for whether the user wants to subscribe. If they do, we'll show the address FormGroup so they will be sent tons of ads in the mail (yay). If they don't subscribe, the address FormGroup will be hidden.
By putting the related address FormControls into a FormGroup, we're making it a lot easier to implement this kind of logic.