Because it's the continuation of SR 210. I was unsure if the non-freeway segment of SR 210 had the same/similar traffic volumes to the freeway segments. However, based on your comment, it appears as if it doesn't, so I won't undo your changes here (that and the fact that I don't live here). Also, you mentioned that "[2100 South] has been bypassed [...] by SR-201 and I-80," but in reality, this segment of 2100 South 𝘪𝘴 SR 201, at least according to Wikipedia.
(Also, you missed some spots)