Maybe. Maybe not. But I don't think that's the reason homebrew doesn't have gcc. The OP is pointing out homebrew isn't extensive, and misses some commonly used utilities.
clang either does not build or defectively builds certain things on OS X, for instance Ruby 1.9.3. I had to acquire vanilla GCC for this reason the other day, and was relieved to find it in HomeBrew.
Old-ass versions of Clang would build Ruby and PostgreSQL (client) binaries which would segfault upon execution. Try grabbing the latest XCode/command line tools package and you should be fine. I've been running Ruby 1.9.3 with Clang for quite a while.
