# Why is End-Of-The-Line defined in terms of "Arithmetic circuits" instead of "Boolean circuits"

The definition of PPAD (Polynomial parity arguments on directed graphs) revolves around the definition of "End-Of-The-Line"

An exponentially large polynomial-depth arithmetic circuit, $$f$$, specifies a graph where every node has an in-degree and out-degree of at most $$1$$. Given that $$0$$'s in-degree doesn't match it's out-degree, find another node where the in-degree isn't equal to its out-degree

I don't understand why we can't just sub in arithmetic circuits with boolean circuits here.