I think perhaps they would have seen more hits/activity if the blogs were an actual "section" in the main forum, a subcategory near "Off Topic" or something, and each blog was treated as an actual thread. Blog posts and comments could bump a thread just like it would if it were a normal thread.
Ex. A thread titled "English Mobster" would contain all of my theoretical blog posts + comments others make on them.
The issue here for their disuse and subsequent removal was probably visibility; other than a couple tiny words below the post count and another tiny link up at the link bar, blogs were never called to people's attention. They had no visibility, people had no reason to visit them, so they were never really sought out.
You can see a similar situation for the models/textures/map release area versus the actual uploading and file hosting provided by the site. There are 10 people online right now; 12 people are viewing the Map Showcase. All of these people are guests, probably looking for new maps to add to their server rotation.
Meanwhile, the actual uploading area that uses the site's hosting system is a tiny link up at the very top. It gets a lot less screen space than the section dedicated to the map showcase, so it attracts a lot less traffic. I know I only use it if I'm looking for a model and can't find it by searching the Model Showcase category; it's just not in my face and visible enough to warrant much attention.
For my first month or two here, I didn't even know it existed until someone posted a link to it. Perhaps you older types who have been here for years use it because it's always been there while I suspect the Showcase I'm used to is fairly new (based only on the fact that there are semi-recent posts in the archives), but coming from a newer (6 months, give or take) perspective, these features don't call attention to themselves when so much real estate is dedicated to the actual forums themselves.
I only mention this because the forum I'm coming from had a similar problem. Nobody was using the blogs or anything that wasn't on the actual forums. Granted, the community itself was dying because the game it was built around was 10 years old and the sequel everyone thought they would move to was hostile for both mapmakers and players due to extreme amounts of DRM, so the only semi-maybe-possibly-active section was the TF2 section (which was really made up of maybe 2 somewhat-active people: Selentic and Jahrain [the guy who made ctf_convoy]). The Off-Topic section was also listed so high on the forum category list that people just went there rather than scrolling down to look at the WIP stuff below it, but I digress.