@Klaas Would you please have a read of the thread from the beginning where I think the justification and answers to your questions were posted?
I don’t have stats for how common it is in the world, just know from my own career: I’ve worked in global roles for companies sizes 400 employees to 130k employees during the last 15 years. Of these, 60% did not allow me to install programs myself on my laptop. For those situations, being able to use Obsidian on the web would make Obsidian usable vs. not usable.
With my current employer, I can install software on my machine (though it is monitored) and the company I’m sure is glad that all my company notes are stored on their Onedrive. However, if I did not have this privilege then a web version would have to be used for the interface (preferably syncing to my choice of provider, such as Onedrive, Dropbox, etc.).