When you represent someone, there are a lot of laws and ethics that have to be followed.
Not any joe schmo can sell his own house. If you sell your own house, your liability for problems with the sale multiply. You can be sued personally for just about anything if you sell it yourself. The other part is most RE agents will not show houses for sale by owner, further reducing your ability to sell your house.
Especially now when the inventory is so high and the average time for houses on the market in many areas is about 6 months. Open houses and advertising can help move the house.