Even today when BTC's value (market cap) still has to grow at least by one order of magnitude, its costs of transaction are too high and its deflationary issuance makes it too valuable to spend.

I posted a noted recently about how in the Euro zone we have SEPA, basically instantly zero-cost transmitted fiat, bank account to bank account. In Spain there's this thing called Bizum, phone number to phone number, obviously linked to bank accounts, but again, free and instant, with a couple of taps on the screen of your phone.

The case for a daily use currency for spending is already covered solved by fiat. Plus, fiat is never going back to the box now that it's out. Not for as long as States exist.

Especially not when Bitcoin devs keep relegating anonymity and privacy, which would be the case for bitcoin use as a replacement of increasingly disappearing fiat cash.