Well because its easier for some to just buy online or sometimes the products aren t available from the shops and also sometimes the people selling the products have sold advertising space to other companies so they are making a profit everytime someone goes onto their site whether they buy something or not :)
To cover more ground /customers, in the physical store only a certain amount of people shop and online you have the world that has acess to your online store. Having potential for business growth outside your physical store.Expansion!!
to sell products. What else could it be?