That is an excellent question. During the H1N1 crisis, everyone thought it was first and foremost a health issue. We knew that we would manage to produce a vaccine. We knew very well how to do it and how long it would take. The big question was in the area of the social sciences: how would it be distributed? Therefore, it was a all about managing the population and the quantities.
In such cases, census data is precisely the type of information needed. That is also the case for a very large number of government interventions, where specific groups or even the entire population are to be targeted.