There are tons of missing blocks that should be in the game that aren't, and it doesn't make sense why.
For example: diorite, granite, and andesite have wall, slab and stair variants, and all of those variant have polished versions, except walls. Why are there no polished diorite, granite, and andesite walls when there are stairs and slabs of that same type, and walls are the raw material. But it gets even more irritated when you see that blackstone and deepslate both have the complete set, including polished walls.
There are plenty more examples, but this reply is already long enough. If you keep an eye out for these inconsistencies, you'll probably find some.