Just because it is time consuming. Nothing else.
There are 4 PCB with 2 ICs each in my project. And all of them are already assembled and interconnected with the main board. New PCB order takes about 2 month in my location. Reassembling takes a lot too, because I dont have a lot of time for this hobby, unfortunately.
So at the moment I'd prefer to look and use the final result. Probably, I redisign it in the future.