Lots of people mentioning collaboration / multiple users, yet all your replies seem to completely ignore this aspect. I’m guessing you might live alone and are struggling to imagine some very common use cases here.

Why not both?

I use syncthing for transferring files around my local network, and nextcloud for sharing files with others.

IMO these are related tools but designed with very separate use cases. Use the right tool for the job.

Ignoring lint issues comes to mind as an at least somewhat reasonable use case.

I just bought a drive from them last month (from Canada) and just received a $60 duty bill. The time before that I got nothing. YMMV