Visibility. My GT trads are four fletched with white feathers, white nocks and 6 inch white wraps with one inch of blood red (burgundy) which is just an individual crest. I tried barred feathers which were not only insanely expensive, but I couldn't see them as well. They looked cool, but visibility is more important.
I agree about the weight on the wrong end issue, but it's worth it to me to see them against fur, especially on bears. I just added more weight on the business end.
Also agree with Huntmaster about making it easy to remove feathers.
To remove the wraps, use a hair dryer.
OneStringer is where to get them.