True, giving users the capability of deleting dead or unused data is usually a "nice to have" rather than a strict need. On the other hand, keeping the volume of a database as low as possible and uncluttered with unused, dead data is also a good principle, and if ever Soren decided he needed to start pruning the database of such, it's a superior approach to let users prune data themselves than, say, to delete the 10% most inactive PCs.
Now I concede I have no idea how much space the character vault actually requires -- kilobytes? Megabyes? Gigabytes? Beats me. Likely it's easier to simply pass around the Paypall hat and buy a server upgrade than to implement a delete character feature. Though it's still a tidy principle