Many of AOL's subscribers are older people who don't realize that they do not need to pay an extra $25 a month for AOL's usually redundant dial-up service. They are not aware that they don't need to subscribe to AOL to get online.
According to Business Insider:
"... [I]f a big portion of AOL's subscribers really are only paying the company because they think they have to to keep using their free email, you have to agree -- this is not ending fast enough."
To help out, Business Insider posted a demonstration showing how any AOL user can quit the service from the AOL Web client.