You don't have to use their software for email of course. Our email address works fine with the mail application using POP3.
Also a lot of AOL people use the software not as an onramp to the interent. (I've not used them for access since about 1996). I do believe that its more the content (believe it or not) that people use the desktop stuff for. This includes things like access to some XM radio channels without actually belonging to XM, the many chat rooms, a fairly in depth library of information dating from the 90s, personal information management, storage and lots of other "community" features. Its actually a pretty long list of things that people could be attached to.
To further confuse things, many of these services are now available from aol.com through the browser as they have moved away from a subscription model to an add driven model. Still not all of these things are and there is no clear information at their site on what version of what you may want for your use.
The marketing staff of AOL that remains probably needs to spend less time sending out resumes and more time looking at Yahoo, Google, Apple and others on how to simplify their customer message and explain what it is that their offerings provide. Watching companies in a downward spiral is rather morbidly fascinating but frustrating too.
The Mac "beta" they put out is another example of the strangeness in my opinion.