Some people prefer to pay their services directly. I would rather pay someone to host my notes, and to build/maintain the infrastructure to host my notes, than hope Google keeps finding it profitable to give me costless storage.
I'm in the camp these days of I would much rather pay someone who does one or a few related things well and charges me for them, I'm already happy with my note taking setup, but 5$ a month doesn't seem too bad for a service I actively use and enjoy.