This is called an online UPS and it's still a thing.
It's not a good option for home use because it's always sending power through an inefficient path. The devices we use have power supplies that can handle transients and fluctuations.
Where is it a good option? I'd expect datacenters to be more focused on efficiency, not less.
Where is it a good option? I'd expect datacenters to be more focused on efficiency, not less.