The ability to create Guest user groups and easily log them into the HAC application can be used in many scenarios. Naturally, the option will not be used by most HA users.
- We have visitors for a long time, access to the HAC application can be helpful in controlling the entrance and presence.
- Our guest goes to the beaches, leaves the Home zone, the TV turns off automatically in his room, which has been left on.
- Our guest is returning by car from the beach to our house. When approaching the driveway, the gate opens automatically for him.
- We rent apartments, access for guests to the HAC application is an advantage of the offer (intelligent apartment for guests). And here we can have a number of automation programmed.
Installing the HAC app for guests so that they can only turn on / off the light in their room is a poor solution. On this point, I agree with @CentralCommand. However, I see more uses for guest HA access.