Why can't unused columns and tables be ignored in a recursive CTE
It's just a matter of order of operations, which is dependent on what the query optimizer thinks is going to be the most efficient execution plan. Yes, we can obviously see that in the end, the final SELECT list only consists of the CatalogNodeId column, and therefore the other columns of the CTE don't matter, so Microsoft probably could've implemented recursive CTEs to be a little bit better with their available execution plans in this regard. But even easier it is for the developer to recognize the lack of necessity for those columns in the recursive CTE, and therefore can be removed from the query, which is generally best practice anyway.