What is it about a natural bristle brush that is different from the regular plastic bristle hair brush?

I am experiementing with less frequent washing as I am getting a bit older and everything is slightly dryer. I thought I would try the old-fashioned 100 strokes a night on each side and see how long I could make it before the hair gets visibly greasy. So far, it takes my hair about a week before I have to wash it. Sorta wondering if less washing means less rebound grease too, you wash frequently and your body ramps up grease production to compensate.