They will tell you what I have allready posted.
According to my cable provider, we have 6Mbps cable. It would simply be impossible to have all the users download at 6Mbps, that would overload their servers and everyone would draw away too much bandwith from eachother which would reduce the speed to a crawl.
In case of (A)DSL, the speed is also influenced by the distance between you and the provider.