I do have one for my family, but everyone seems to forget about its existence when I don't mention it. So I am the only user right now.

Yes. Personal an family. Sharing calendars, backing up contacts from android. The occasional email attachment upload etc.

I also use it to take notes, manage recipes and todo lists and more aspects

Mainly personal, but currently also for me and my fellow group leaders in my local scouts troop. And I'm planing to spin up a nextcloud instance for the complete troop. Is better for data privacy (especially in regards to GDPR) than most other file sharing sites, which often will send data to the USA. And the shared calenders will also be helpful. I also investigated for an online office system connected to it (like OnlyOffice or Collabora), but the prices for everything above normal personal use is just too high.

For family use in my case, via docker compose on a Nas. But currently we only / mainly sync multiple calendars, personal contacts for each member. Additionally we utilize nextcloud to sync new photos and keepass files from phones to personal folders of the Nas. Aside that we don't use any apps as the Nas lacks some CPU power and ram.