My impression is that it matters because if the data hasn't been collected with a specific purpose in mind, then its probably not gonna be useful for a lot of c

My impression is that it matters because if the data hasn't been collected with a specific purpose in mind, then its probably not gonna be useful for a lot of cases. Say I'm a farmer and for examples sake I want regular aerial images to estimate crop yield for a plot of land. That would require high resolution imaging of a particular patch everyday for maybe a few months. That would require purposeful data capturing at regular time intervals during overhead satellite passes. From what i understand satellite imaging companies won't happen to just have those images containing the region of interest you want just lying around on their hard-drives which they can pull out with some query. If they make all the images they have available to the public, I'm guessing most of it will be useless to people considering it needs to cover the desired region of interest across time and space.