Other clubs don't seem to go through troughs like we do. Carlton haven't won in yonks, neither have Richmond, yet they still get more members than we do. I know they always have had more supporters overall, but strings of losses don't seem to impact much on their memberships.
Two things have to be taken into account with membership. Overall success off the club (Premierships) and average win/loss ratio for the life off the club.
Our win/loss ratio is lower than most clubs and our premierships are lower.
I'm sure if you compare ours to Collingwoods/Carltons/Essendon you will have your answer to why we have low memberships. I would say at a guess the likes off carlton/collingwood have 30,000 odd thousand real members with between 10,000 to 15,000 floaters.
We probably have 3000 to 4000 floaters who buy or don't buy depending on how we are going.