Well, typography is often about readability. Removing the word boundary in compound nouns isn't really helpful since it removes a boundary that conveys meaning.

There were some examples of nouns where you should avoid ligatures in the TeX docs iirc. Shelfful and selffullfilling are the only ones I remember.

In German (every single fff on any page that bothers to set their own fancy-pants font) and swedish text you see it all the time, often coming from self-proclaimed typesetting/font nerds.