[Omni5cience]

On a related note, I recently found out that all SIM cards run JavaCard applications. Apparently SIM applications are not uncommon in countries where smartphones still aren't common.

Check out https://simhacks.github.io/defcon-21/

[praseodym]

Indeed, SIM cards in third-world countries seem to be the only place where installing applets on a third-party smartcard (i.e. the telco's SIM card) is commonplace.

Smartphones are only recently catching up through the addition of secure elements in the device. Without them, the SIM card is the only place to securely store secrets.