There is always some amount of risk that a new technology will make all your investment worthless. The most extant example of this is the US telephone system: billions invested to have a copper wire in every home which is pretty much useless now (and appears to be a reason why US operators charge such high rates). Countries like India and many African states are bypassing this investment in infrastructure by going directly with mobile phones. Does that mean that the US should not have invested all that money? No! The system was very useful while it lasted; there was a demand which it satisfied. It made its owner ATT immensely profitable, and gave it enough legroom to start a research lab where eccentric geniuses could hack away on projects that would be so much more useful than what anyone could have ever imagined
High speed Internet access whether DSL, cable, or ethernet requires "a copper wire in every home" [ok, fiber requires a glass wire, but it's still the same concept].
The wires that were run for telephones aren't always appropriate for high-speed usage. When you have to design for lowest common denominator this becomes a real burden.
