Thanks, everyone.
I think I will put them in, at least for referencing what would be common in certain areas, and to provide some useful encounters with local people and things. I like the idea of using a couple dice to get a nice bell curve of low CR's that would be encountered more often.
As a side note, would having more encounters of lower level monsters become boring? It does add realism with the fact that there would be more of them to go around and only a few of the big monsters in the area, but would that slow down play and/or make the players bored. Say the party is higher level and is still running into goblins every time they enter the forest. The players know that they are there, but they might want to speng gaming time on something more challenging.