The bright color can sometimes allow you to see a strike that would otherwise be missed.

I read an article a year or 2 ago where the author was fishing in slow water with a lot of algea and such on the bottom. He noticed some small aquatic worms in the algea and examined some of them. When he dropped one at the surface of the water, it curled up just like a green weenie. At the bottom, it unfurled to the protection of the algae and rocks. He tried this with more, and each did the same. This was apparently an evolved behavior to quickly sink to the bottom to reduce the likelyhood of becoming an aquatic lunch.

I doubt that every fish that takes interest in a weenie has these worms around, but it is at least interesting info.