Because you're not supposed to...?
Since you can't even provide me the username of said member, I can't really explain why they would have blogging permissions. Perhaps they used to be staff, but even so, they wouldn't be able to create new blogs since the date they were demoted. The administration does reserve the right to hand blogging privileges over to regular users for special purposes, but this has only happened a few times before, and the results weren't satisfying enough to allow any new users to gain the priviledges that way.
You gotta get 5,000+ posts, donate to the community, or become a member of PokéCommunity Staff before you can blog. Simple as that.