systemd-inhibit fails to stop system from suspending

I’m trying to suspend my system using:

sudo systemd-inhibit sleep 43200

However after my system is left idle for a while, the screen goes blank and it gets suspended. Why does systemd-inhibit fail to stop my system from suspending?

According to the doc it should inhibit a system suspend state:
https://www.freedesktop.org/wiki/Software/systemd/inhibit/