Unfortunately Google Fi has its own set of issues that make it unpalatable as a primary mobile phone service: https://onemileatatime.com/google-fi-review/

I believe this is around when Google Fi expanded to support iOS? I think there were some admitted growing pains around that time, and they've worked to improve it since then. Hard to say.

> This is a nice benefit of Google Fi. Since swap attacks are not possible with it, as customers support agents aren't able to do sim swaps.

Are you sure that this is the case? According to https://support.google.com/fi/thread/761170 there was at least one case where support agents moved a Fi number from a locked account to a newly reopened account, without the user being able to access the locked account:

> I call Google Support and the amazing Google Support rep I spoke to (The only good one I’ve talked to so far during this whole process) stayed with me for over an hour and worked with tier 2 support in getting my Project Fi number transferred to Account 2.

A SIM swap with Fi might be harder to accomplish than with a regular provider, but it looks like there's still the risk that someone manages to convince a support agent to move the number to a different account.

What happens when Google spontaneously bans your account for no reason?

What do you think happens?

Having unempowered customer support agents may mean customer support agents can't take over your account, and can't be social engineered into taking over your account. But it also means people who only have a phone and lose it with the sim and also don't remember their password (perhaps because it's never prompted for) are going to have a hell of a time getting their account back.

Is there a guarantee that Google won't add this feature in the future? What if people lost their phones etc.?

I think the risk is too big. Use U2F, or something similar.

If you lose your phone you simply contact customer support to mail you a new SIM card (Not sure how it works with eSIM, but I assume something similar)

I'm guessing this likely also applies to a Google Voice account phone number.

What happens if the SIM is damaged, lost, or stolen?