/etc/fstab is parsed by systemd and converted int .mount unit files, so that they can be mounted when a) asked for it (auto/noauto) and b) as soon as possible.
think of the _netdev flag: it signals systemd that a mountpoint is network-based, and thus it will attempt to mount it only after the networking target (instead of waiting for it to timeout at boot time, fail , and possibly letting processes start reading and writing from/to an empty directory).
Running daemon-reload is generally system(d)-wide though: whenever systemd configuration is altered (think adding/removing/updating an unit file) you should let systemd know about that by running systemd daemon-reload (think of apachectl reload).
"Long time" is also relative. I've been updating /etc/fstab directly for over 25 years.
Yeah... there's always a "good reason" with systemd, isn't there?
Still doesn't account for the lack of error message.
After poking the internet:
So, the summary with systemd: it will break something for everyone sooner or later. It hopefully won't be something you can't fix, but it will make you very angry and in immediate need of a tea break.BTW, this is not the first one for me, but certainly one of the most frustrating ones, and not because of the behaviour: because of the lack of error messages on stderr or at least in syslog. The messages in ~~syslog~~ journald were casual.
[^1]: https://unix.stackexchange.com/questions/169909/systemd-keep...