For small teams, the ability for people to jump into a conversation which began without them can have value. If you are a 6-person team, and when two engineers

For small teams, the ability for people to jump into a conversation which began without them can have value. If you are a 6-person team, and when two engineers say "Hey, we'll probably need a design for this", the designer can hear this (if not in deep concentration) and join the conversation without any slack messages needed. This sort of 'free triage' has some value, not sure if it's net advantage when accounting for distraction costs though. Price is probably the clearest advantage: you can fit more people into an office without walls.