That's one of the downsides about folding to be honest, If everything is running fine most folders just see this as a blessing and carry on doing other things. The only time you'll see new posts is when someone is testing new hardware or has a problem etc.
To be honest i only look at folding forums once or twice a week and even then its a half arsed look.
Why do people lose interest? depends on the person, but chances are its money vs electricity cost that kills it for most, the rest that start then just stop well they were never really interested in the 1st place and just felt like jumping on the bandwagon without fully understanding what it was to start with, just like a friend of mine who used to call me for wasting so much £££ on it without him fully understanding it then one day he started and made such a big deal about it then a week later because he didn't see mega points or mystery prizes??? he just stopped and nothing was mentioned again lol.