How is that single man business has not been entirely obsolete even under modern conditions of trade and industry?disscuss

in the sole trade all the activities like sale ,purchase, production and marketing have to be performed by the owner itself . now, here he cannot appoint managers as there is limited resources in sole trade so he have to do all the things by himself. generally no single individual can do all these activites accurately, surely there will be some problems have to face to the owner and with this business get unbalanced