This is exactly true. In my city, there are only two ISPs. Insight (TWC), or a really crappy DSL provider.
In many areas of the city, the DSL provider has made exclusive contracts with newly built apartment complexes, where those complexes will not and can not run cable lines, thereby forcing residents onto the DSL provider for TV and internet.
This is done because the DSL provider is terrible and would be unable to retain customers if people were given a choice.