The unit files have no installation config (WantedBy=, RequiredBy=, Also=,
Alias= settings in the [Install] section, and DefaultInstance= for template
units). This means they are not meant to be enabled using systemctl.
Possible reasons for having this kind of units are:
• A unit may be statically enabled by being symlinked from another unit’s
.wants/ or .requires/ directory.
• A unit’s purpose may be to act as a helper for some other unit which has
a requirement dependency on it.
• A unit may be started when needed via activation (socket, path, timer,
D-Bus, udev, scripted systemctl call, …).
• In case of template units, the unit is meant to be enabled with some
instance name specified.
Already the copying is likely wrong - from the same docs linked above:
[…] If your distro provides the systemd service files for Syncthing, you can skip step #2 when you’re setting up either the system service or the user service, as described below. If in doubt, try if it works without and go back to step #2 only if enabling the service failed.
(Skip if your distribution package already installs these files, see above.)