I would like to ask you breeders why some of the labrador's coats are soft and some are rough and coarse feeling?

Because some are correct and some are not.

From the AKC web site on Labrador Standard:

Coat
The coat is a distinctive feature of the Labrador Retriever. It should be short, straight and very dense, giving a fairly hard feeling to the hand. The Labrador should have a soft, weather-resistant undercoat that provides protection from water, cold and all types of ground cover. A slight wave down the back is permissible. Woolly coats, soft silky coats, and sparse slick coats are not typical of the breed, and should be severely penalized.

Bathing can cause the coat to soften a bit and if the dog has been spayed then their coats tend to change a bit.