Do you want people to know when you're at home? Fairly easy to do from electricity or water usage patterns. Supposedly only the utility supplier would have that information, but they are so incompetent at security, who knows who else? Certainly the police have access to that. Looks like a sensible security measure to avoid that exposure.
You can also drive/walk past in the evening and see if the lights are on inside.
Snooping a smart meter signal wouldn’t give away much more, and would be much for effort for a typical burglar
