I think 99% of email users have not been adequately trained in why or how they should report spam, and even if they were I think most of them would still not care enough to actually do it with any regularity.

When pushed many may acknowledge that they know it exists, they will probably even be able to find the button when asked if given a chance. But they won't remember to do it when they see spam, they'll just ignore it and move on to the messages from people they know.