Eh those rules seem dumb and are in some ways... but as someone who moderated a roughly 200 and 250k subscriber subreddits for around 6-7 years, I can say from experience that an insane amount of people just tried using the platform to shotgun links to their bullshit youtube channels or content mill tech blogs.
You'd see one of those links, look at their profile and sure enough they just had a huge list of them firing off the same link to 10-20 subreddits, then the next link, then the next. No discussion, no commenting history in those subreddits for the most part. They were just using them as a way to get clicks and nothing more.
Left unchecked, that shit destroys the quality of a community. I know because the first big sub I grew from about 10k to 250k had been left open to that stuff for years and had totally stagnated. As soon as I started cleaning house the place blew up in numbers and quality of content.
The vast, vast majority of people linking their own off-site content on reddit (in my experience as a mod) was definitely people just spamming. And if you let them do it the subreddits go to hell.