You can use for: government interaction, banks, utilities, health records, and lots of other things.
They also made a digital secure mailbox, where you can receive PDFs from government, banks, utilities, doctors, etc. You can also send replies.
It sucks that all of this is point-and-click web apps without a standardized API. I'm sure other countries have similar things, but most implementations are probably snowflakes.
Whereas email is universally integrated everywhere, it's not trusted for personal sensitive information.
I hope one day secure webauthn and secure email will replace all these snowflakes. But as much as I hate to admit it, the non-standard walked gardens does do a better job, with higher security than the old paper world ever did.