Exo planets and player rental planets serve two very different purposes.
Exo planets were introduced along with new items & are a large chunk of content for the game now. It allows them to experiment with special planets too, like the recent color-changing one. Several times, there have been long droughts with no Exos or no T7 Exos.
People are renting planets to have their own personal space for building, guilds, control of certain aspects, etc. Just like clubs/guilds/land/etc in any other similar game.
One type of content should not suddenly negate the other without reason/explanation.
We can only speculate as to why the drought is happening. At least once previously, it was due to other content/updates that they were working on.