When working in-office the office becomes the communication app of choice. Walking over to someone and tapping them on the shoulder to ask a question. The water cooler chat. The impromptu meeting.
Those habits die hard, but for a team to be successful working remotely requires that communication shift to another app, usually your enterprise social network (Teams, Slack etc.)
If you decide on a hybrid model (some individuals in-office and some remote) it becomes especially important to decommission the office as the communication app. If you don’t you will severely disadvantage those who are remote.
In this situation everyone (co-located and remote) must use the same communication app or you will lose cohesion.
This all paves the way to the next level of efficient remote working - becoming an asynchronous-first team.