Earlier quoted context omitted.
Assistance != taking over. It's driverless by definition because... there's no driver in the seat. The car is in control and is responsible for its safety at all times.
Regardless of the definition, I can't buy and own such a "driverless car" because I don't operate a supervision center with people available to "assist" the car. Whatever "assist" means. Nor can any company that's not large enough to operate the infrastructure. I'm sure at least some of the hype is in regards to people owning such "driverless" cars. It's driverless by definition because it does not have a driver, but…
If you fall asleep or don't respond it's fine, you're just stuck.
I don't think Google plans to do this for a variety of reasons, but I don't think there's fundamentally any reason they couldn't.