Isn't asking people where they would like a new subway line a case of asking people what they think the solution is rather than what problem they would like to

Isn't asking people where they would like a new subway line a case of asking people what they think the solution is rather than what problem they would like to have solved? Wouldn't a survey of what journeys people want to make be better? Sure, processing the results is hard, but in the grand scheme of building new transportation in SF it's trivial.