Syncing files is only one of its capabilities. It is best suited for use between two individuals/organizations that need to transfer files between themselves more than a few times. Its main advantage for me is that it doesn't require a central storage system, such as Dropbox, to hold the files. It's just you and me and a rendezvous server.
In a previous life, I used Syncthing to transfer terabytes of files from the company I worked for to a third-party printer. It was delightfully reliable, and easy to set up.
If it's a one-off, yeah, you're right that it's not wonderful. I've used Magic Wormhole successfully for that use case.
[1] https://magic-wormhole.readthedocs.io/en/latest/