Intentional disconnects are used by Service Providers to free connection hardware tied up by users who are leaving their connections idle. We can't explain our problem solely by intentional disconnects. In some cases, we see line drops after connection times of less than 20 minutes. In other cases, we see line drops even when the line is not idle. It is when you consider costs.
Users generally pay at least ten times more for full time dedicated Internet connections.
Since the general marketplace supports this difference in fees, it is safe to assume the difference in costs must be real. Service Providers simply can't afford to have their individual dialup phone lines turned into full time connections. There is no universally accepted answer. However I can't blame Service Providers, at least the ones providing unmetered service, for utilizing intentional disconnects to keep costs under control. Sorry to say, the excitement faded when others made the same change, but continued to experience unintended disconnects.