Good to know. Why is it a root daemon and not a command/library if other tools are directing it? If I had to guess, so the end user does not have to elevate to superuser to initiate actions?
The other main reasons is that some hardware is really, really slow (like 8 seconds to query a dock PD version, or 12 seconds to query a thunderbolt retimer version) and you can't really build a GUI that can do firmware update operations with potentially minutes of delay for each action. Also, cache invalidation is hard if you can't see the device uevents and usb hotplug events.
(Thought I'd seen a GUI for firmware but can't find it at the moment.)