A Relic of a Bygone Era
Companies used to pay to host their support and user forums on Compuserve. That for example is how Siemens used to do their on-line support and user forums for their industrial automation division. Siemens maintained them on Compuserve long after the Internet became the mainstream and walled garden networks such as Compuserve were otherwise a relic of the past (Siemens rarely saw a bad idea they didn't like). I can remember people having to buy Compuserve accounts just to get support from Siemens and for no other reason.
Aside from cases like that however, people cast aside Compuserve, MSN (the original incarnation), and several others I can't remember the names of, gladly when Internet service became generally available. With the Internet you could talk to anyone, anywhere, instead of just within your own providers walled garden, and not have to pay ridiculous extra fees to access Internet email.
Large corporations contracted their external email services through these companies. If you were "in network", you could send email to other companies readily enough. If your email needed to go out to the Internet, then you had to pay extortionate per-byte charges to use their Internet gateway. The real money was in these email services, the forums were just an extra bit on the side to encourage individual users to sign up and so create a critical mass of users. Internet gateway charges were kept high to try to keep their own user base inside the walled garden.
After a while having a Compuserve email address became the symbol of being a dinosaur. Large corporations also had their email service provided by them and other similar companies. You could tell which ones those were by the bizarre email addresses. I think that there was even a Dilbert cartoon about it.
Once enough users were on the Internet, the user base for Compuserve and their ilk started eroding due to a combination of cost and access to content outside the walled gardens. Without the email services which hauled in the cash, the whole business model fell apart. Even Microsoft were forced into a humiliating climb down and admit that MSN was never going to replace the Internet and so shut down MSN (later re-using the brand name for their Internet "portal", back in the days when those things existed).
Having gone through those walled garden days, all I can say about the people who think it's a great idea today to re-create those days in the new walled garden services of today is they are utter retards.