Some people have valid reasons for using 56k, such as living out of the range of broadband. Most, however, are just too cheap or stupid to buy something better.
My girlfriend's dadworks at home on Ebay over his 56k Internet connection.
something poor people use to connect to the interweb. It's slow as shit and uses a phone modem. It forces you to do this strange "dialing up" thing before you get on.