It’s a very good point. There’s no question that central scenes are much more powerful than direct association, and we are seeing more and more devices using those command sets.
However, there is still one thing that direct association can do that central scenes cannot, and that’s make sure that the desired linkage still works even if the hub is not working.
That can be particularly useful for a virtual three-way with light switches. It’s not something you would ever want to suspend, so you don’t need the extra features of central scene management, But it does mean the auxiliary switch will continue to trigger the master switch even if the hub is unavailable.
Smartthings has had an Outage at least once a month for each of the last 18 months except, I think, January 2017. In addition, they can and do push out maintenance updates typically a couple of times a month, which customers can neither refuse nor delay. These take the hub off-line, sometimes only for a couple of minutes, but sometimes for several hours. So many people do use direct association as part of their outage planning, particularly for virtual three-way lighting set ups. So the feature remains relevant.