This question already has an answer here:
The Infrastructure Master role is responsible for updating references from one object to another in remote domain. It compares it's data with the GC. So it is dependent on the GC.
Is it possible to assign Infrastructure Master role to a GC server?
my question is that Microsoft could unite this two roles together and the infrastructure master role is not necessary and the GC can play infrastructure master role . Does infrastructure master role have any other responsibility except updating object references ?