Comment by Avamander

Some countries turned it into a part of their national ID system. Has worked great for the past 15 years. You can get a card reader for less than 20€. Works under any OS really. I can't remember the last time I got physical mail that wasn't some item I ordered.

S/MIME died because it is in many ways worse than CDOC and ASiC-E containers over email. People are reviving such approaches with EIDAS2 and from that ERDS (Electronic Registered Delivery Service). But there are no EU-wide implementations as of yet.

Those app-based approaches have also appeared, because well, they don't require a card reader. Though I'd rather see something NFC-based with a physical card. I personally find phone vendors' HSMs (and their equivalents) haven't seen enough scrutiny. Plus the apps are proprietary.

The demand is definitely there, but I predict it'll take at least a decade for the rest of the EU to catching up to Estonia, Finland and a few others. Just 25 years later.