It matters because it takes resources to generate power, even if that's just to build the wind turbine, given we've got a limited amount of any resource then using it just to allow everyone to travel in an ineffective way isn't the best way. Especially given what I said this morning about the energy requirements of the vehicles in the first place.
Well the resources necessary to build say, a nuclear power station, are not in any kind of shortage. They consist of concrete, steel and aluminium - all of which are available in functionally unlimited quantities.
The inputs are also negligible compared to the amount of energy that will be produced over the lifespan of the plant.
There is also no uranium shortage, or any prospect of their ever being one - even the currently far too expensive seawater extraction of uranium is sufficiently cheap to render the maximum possible price of uranium irrelevant as to the price of nuclear energy (and before anyone says it is far too expensive, just ignore the idiotic deal the government signed to avoid the appearance of state ownership at Hinkley)
That's not too say that we should force everyone to use public transport, rather there's good reasons to encourage it's continued use.
However, subsidies to public transport and such (including deliberately restricting the utility of road transport, such as forcing the deletion of a road crossing of the Irish Sea in favour of a rail only solution) also represent a cost to society, which is in many ways comparable to the energy "wasted" by less efficient means of transportation.
The only way an Irish Sea crossing will ever come close to defraying the cost is if it as a drive through road solution - the Channel Tunnel has been a commercial failure and has been unable to even drive the Dover-Calais ferries out of the market.