Because sometimes its easier to sell stuff on ebay....i know when i tried to seel some stuff on here people would say well im interested and then they would never purchase the item. On ebay if you bid on the item then you have to buy it unless your out bid by someone else.....Also if you look on his ebay site he has more GM parts to sell.....so i think he decided to sell it all on ebay instead of spreading the parts out to different sites....Just my 2 cents...