Why only stock android based custom Roms? Why no porting??

While I really appreciate the work put in by the developers for Zenfone 2, I don't see any ported roms from other flagship devices like any Note Rom, Miui Rom, Sony etc. ?
If any of the developers is listening, please port some roms from other devices, it will be a good change and new experience for our amazing Z2. Thanks !!! :D