I imagine it may be because POSCON is still in its early development stage without the ability to really get 'hands on'.
There was a lot of chatter, even a store page on steam about 'ROTATE' prior to its abvoius money grab kickstarter and subsequent demise for not making its $100,000(I think) target.
Some people were looking forward to a June beta that has been pushed back to a end 2018/early 2019 date. I understand development takes time but I really think you guys missed the summer influx of pilots/ATC that the other networks get, also with FSX/Xplane in the steam summer sale.
As I only really do my VATSIM ATC streams I'll be trying out POSCON once it goes publicly live but an aggressive marketing strategy prior to it should be done.