Reference counting is GC - or rather it solves the same problem that GC solves. I don't see why people don't count it as one. Sure, basic reference counting cannot handle cycles - but there are extensions that can.
Sure it is GC, the very first chapter in most CS books about automatic memory management starts with reference counting and then proceed to more elaborate algorithms.
It is usually presented as a quick solution for when the resources for doing more powerful GC algorithms aren't available, either in computing power or engineering.
