wb_entity_per_page maps entity IDs to wiki page titles. Since we have, and very likely always will have, a programmatic mapping from entity id to page title, this is not needed. Also, wb_entity_per_page in it's current form does not work with non-numeric entity IDs.
If we remove this table, we can no longer use it to iterate over all entities. We would need to rely on iterating wiki pages by namespace and/or content model. This does not seem to be much of a problem though.