At level 71, you unlock the last Elite building, the Manor. At level 6, it adds 100 to your pop limit and uses the same building space as a Noble Residence (which has a pop limit of 80 at level 6). But... it takes a building licence and there's no corresponding gem version that doesn't use a licence. Now, I don't like to generalise, but I'm reasonably confident that no player at that level is using any buildings that consume licences for population. Most of us I'd imagine are using a combination of merchant bought Nobles, Mag Residences, and various loot buildings (Frozen Manors, Witch Towers castles of various colours, etc). Certainly I can't see anyone wanting to dedicate enough licences to make a significant dent in their pop limit in this way (I have around 150ish Nobles, there's no way I'm going to sink 150 licences into replacing those).
On top of that, it's also fairly likely that players at that level no longer care so much about increasing their pop limit anyway. I have a pop limit of around 27k, I keep a standing army of about 25k troops and I can easily run a bunch of fairytales or ABs back to back without needing to wait for more troops. I know of some players with more than 35k pop and I can't imagine that increasing that number brings a lot of benefits for them.
If the Manor didn't take a building licence then I could see that it would be a useful upgrade over the Noble (with a corresponding hike in production and upgrade costs to balance it obviously), but as it is, it just seems pointless.