Because the point of removing off topic material is to help facilitate discussion and having 6 "real" posts and 5 "<removed> posts doesn't do that.
I like to do the <removed> posts when someone has posted something objectionable/reported it so that the people that wanted it actioned can actually see that it was actioned and as a visual reminder to other posters that they should be following the rules.
Having 1 post removed and thinking maybe something weird happened so you repost it. Yeah, I could see being upset with getting a sudden ban. I could even see it if it happened twice. But after 4 or 5 posts of the same thing being posted and removed, its pretty clear that Binar wasn't randomly trying to post a forum trope and was suddenly banned for no good reason. If he wanted to ask me why I was deleting his posts I would have been glad to tell him with no action needed.
I banned someone for 24 hours for spamming off topic posts over 3 threads. It's not like I perbanned him for saying Taylor Swift is a [content removed]