Many people are in situations where task stand up and tear down are the most expensive things in their universe. If something comes up after you have spent 20 to an hour standing everything up but you need someone to do one thing, context switching will be brutal. If you are in the same physical location at worst case you can go find them, or you can ask around to know when they are next available. If they are 100 miles away on slack and not responding or otherwise not being able to get a hold of them, you are blocked and now have to swap to something else.