Ever since the 1972 settlement there have been attempts to make it all better. Always half-hearted, frequently half-baked, and never completed, these occasional skirmishes have left the map in a mess.
Generally, that's ok though, isn't it? Because we all manage to get by, don't we? And since none of those reforms was a serious attempt to answer the question of what English local government is actually for, a complicated and mildly chaotic structure is really just quite quaint.