Users often download huge files, or access Web sites with substantial graphics. If the bandwidth isn't available, there are significant delays, causing significant losses in productivity. That's near T1 speeds for a very affordable price. Easy to manage. Today's economy is extremely competitive.
Few companies have the luxury to burn expensive internal cycles on managing their Internet access.
Those cycles are better spent growing the company. These servers are typically used to sell products, generate leads, or host internal applications. Managing a large network of users who constantly access the Internet. The major difference is that the service is designed for sustained usage. At Home Corporation.