Life is not always just black or white. Sometimes, there are also some shades of gray. For some cases, streaming replication might be just perfect. In some other cases, file-based replication and PITR are all you need. But there are also many cases in which you need a bit of both. One example would be like this: when you interrupt replication for a long period of time, you might want to resync the slave using the archive again instead of performing a full base backup. It might also be useful to keep an archive around for some later investigation or replay operation.
The good news is that PostgreSQL allows you to actually mix file-based and streaming-based replication. You don't have to decide whether streaming-based or file-based is better. You can have the best of both worlds at the very same time.
How can you do that? In fact, you have already seen all the ingredients; we just have to put them together in the right way.