I've not seen anything on the C:S wiki or in-game to suggest that having pass-by traffic is either necessary or desirable for commercial properties (noise is listed as a negative factor, so traffic can be negative). However, this is one of the key metrics for commercial realty in real life, so it seems odd that it would be ignored in an otherwise fairly realistic sim game like this one? It was a factor in SimCity 4, for example.
Does traffic, specifically commuter "people" traffic not freight trucks, encourage commercial properties to grow? Will they stagnate or be abandoned if, for example, built on a side road away from traffic?
(Yes, I could test this, and I will if no one has a canonical answer, but there may be confounding factors that I as a newbie misunderstand. I'd love to know how the engine works.)