Identity theft, regular theft, harassment, stalking, sexual assault, discrimination, reputational harm, etc.
Example scenario:
I tell a friend that I voted for Trump, my Google home hears it, a Google employee eavesdrops, leaks on twitter that I voted for Trump along with my home address, the likely times I'll be in my home, and even the pin to disable my alarm, etc. Then a group of left-wing extremists uses that information to harass/rob/murder me.
Alternate scenario:
Google employee uses their access to find an attractive woman with a Google home, steal nudes, spy on conversations, etc. That escalates into stalking, and eventually sexual assault and/or murder.
Both of those scenarios are possible today, and we're just supposed to "trust" Google is being responsible because they say so.