@Plaguescarred on twitter
From WotC's perspective...a) each character consumes a certain amount of storage. The cost of this storage is pretty cheap, but nonzero.b) if we had unlimited storage we would store a great many theoretical builds, abandoned attempts, every level of a character (including theoretical builds) as a separate entry, etc. By limiting us to a small number of characters, they tilt us more toward storing (on their server) only the characters we actually use. They (by intent, not necessarily actually) look at all the characters we build in order to see what people are using, and having fewer theoretical builds and less undiscarded trash gives them a more accurate picture.Granted, it's still mildly annoying.