that's not an automated update at least for any self respecting software developer. Download the normal installer and run, really? That's the best you can come up with? Forgot about delta updates, dealing with conflicts on OSes such as windows where resources in use can cause installations to require reboots. Permissions issues, updating software that is installed with system permissions from software running as a non-admin user is not as simple as download a file and run it. Debugging failed downloads/updates and providing support for them. Non-standard installations, for example binary installations, vs distro packages vs run from source setups. Hell even detecting that calibre is running in order to shut it down for an update is far from trivial, since calibre has about 20 different binaries, many of which can run concurrently with the main program.
And what part of "I dont want to rely on free services for calibre hosting" did you fail to comprehend? Did it ever occur to you that I might have relied on free services in the past as primary hosting and been burned by them? So no I am not paying out of pocket for fosshub and github, though I fail to see how that is relevant to anything.