Firstly, I really like the inclusion of Essence into the game. It's done a lot to keep City Enchantment madness under control.
However, when a settler builds a new city on a tile w/o essence yet is adjacent to an essence tile it's baffling to me that even though the city you're building upon encompasses an area you KNOW contains essence, you are never able to benefit from it's being under your sphere of influence.
Why not build it on the essence tile in the first place you ask;
- There is a single spot in a field of buildable tiles that has the ability to provide essence and another player has parked a unit on top of it so that you cannot benefit from it
- You would prefer to create your settlement closer to a river/forest/terrain tile as it gives you more strategic benefit over where the essence tile is
- Building on the Essence tile would close out all of the other buildable tiles in the area
If possible, I would prefer to see a settlement gain the benefit of the best essence tile in/adjacent to the settled tile, this would in most cases correct the problems posited above.