Porting os course. It takes too much time to port various stuff from rest of world.
It takes too much time to prepare software env. before You can start coding.
OWB for example.
You can't just take sources and start playing with code.
To compile it You need more than ten addidtional libraries.
Disk space is cheap today.
Even if unix is bloated so what?
This "bloat" saves developers time.
Going to x86 should fix this problem.
MOS/Amiga Os on x86 should be based on unix.