Not everything's going to just spring up and demand a place though. History isn't a popular trend or a media type- it's a serious subject. Like I said, looking as both a first-time poster and even now over a year later, I took one look in the General Forums and said "Nah, not posting anything really intelligent in here." It had nothing to do with it generating interest and everything to do with it being buried instantaneously about topics like "Wu screwd wu in teh show!!1/1??" and "arbortoin r teh wr0ng!!!" within the first hour. Most browsers are going to take in at a glance the first page-full of data they see and make a decision whether or not to post. If it's consolidated into one subforum, there's less crap to sort through to find chocolate.
In America, voting is simple. But less than 60% of voters vote. Why? Voter registration was the main problem. It was a simple process in itself, but it was one more hurdle and the public wasn't interested enough to put that kind of effort. This is the modern communications era- they wanted to hit a button, pick the guy who's securing their pension, and go home or to the bar.
Same mindset here- browsing is really simple. But when you can't browse at a glance and isolate topics you want to work on, it suddenly goes from hopeful to "Eh, I ain't doin' that" mentality. With 80,000 members or more, I'm sure the subforum will generate interest.