It's not an idle fear. Before https there were ISPs that would literally insert ads and other javascript into returned pages. Beyond security itself, that kind of thing can break the content.
There was also content filtering. Imagine your home internet being scanned and filtered like some locked down corporate network. Ewh.
To be fair, a lot of those consumer rights had to be realized and invented first - after the corporations went too far. Think GDPR and co, if companies weren't so thirsty for danger and loading webpages full of trackers, it would never have (needed to) be made.