Because Facebook increases your web presence.
This is the most basic reason for you to do anything online, because it increases your web presence. Any business has only one objective, and that is sales, be it a product or a service.
Businesses are always looking for ways in which they can get exposure without spending tons of money and the web is giving us that opportunity. More than 75% of the population in Western countries has broadband connections at home; more and more people are going online for their needs. You must take advantage of that.
Amazon is posting a 15% growth each year, and their profits have skyrocketed in the past couple of years. In fact, even during the downturn, they were one of the few industries that posted growth. There are a number of benefits to buying online, primary among them being lower cost and this benefit is hard to match in retail.
Because you can take advantage of the place where your customer gather to Network
Because you can take advantage of the place where your customer gather to Network