Just because one doesn’t see the point doesn’t mean one doesn’t exist.
Each communication tool has its strengths, namely managing interruptions.
People using one’s attention as their inbox directly with DM vs a when you can get to it email can be easily mismanaged.
It’s different for each job.
I also find my SMS/iMessage increasingly polluted by companies that have probably discovered that their emails are filtered automatically or otherwise and no one responds to them any longer.