Unlike the carriers, they won’t just hand your line over to anyone who asks.
Rivers of cheap data when you’re traveling.
If you’re in San Francisco on an iPhone, then Google Fi is just the T-Mobile network. Which is good to remind us what life was like before phones.
International data including at no additional charge (and not rate-limited like Verizon & AT&T) and secure to prevent SIM-swapping attacks (you need access to your Google account to make any changes, even if the changes are over the phone).