Because this is the elite board where only(well, mostly ) the mature people go and everybody else is scared away.
We're so elitist, none of the cool kids want to play with us.
I haven't played a Total War game in a while either and I'm not that into mods so I hardly see any reason to go to TWC, but other people do as they love modding etc. and I think the site offers a bit more space for modders to upload files etc.
After seeing some of the discussions there I didn't find it too appealing though, the org may have strict rules that many don't like, but I prefer this friendlier atmosphere here.