Cable companies these days are aware of the security risks involved with cable (both TV and data)... which includes wiretapping, eavesdropping, etc...
Plus, with proper traffic routing techniques, more subscribers can sign on with little performance degradation.
DSL happens to be distance-limited, as if you live within the cutoff point (~18,000-22,000 ft. from the CO), the best you can settle for is 144K IDSL, and performance usually gets better the closer you are to the CO.
To make it more bearable though, SDSL happens to be good for hosting servers (HTTP/FTP/games, etc.), due to lower latency than asymmetric lines, but even so, the cost for a 1.5Mbps connection (both ways) is still quite high.