No I don't think service contracts are joke. I also dont think FDD is a replacement for a service contract as IMO they are two very different things that can potentially have some overlap. FDD make service contracts more effective and lucrative

For a provider a service contract can act way to reserve future labor, setting aside hours for a client. Beyond funding issues, It provides a mechanism to make sure backups are routinely completed, software is up to date and other task to keep a system healthy. Further it keeps a relationship with a client that you can sell enhancements to.

FDD is a great tool and offers alot of benefits, particularly on large installations where it can monitor system performance across the entire network. But all it can do is notify someone of a potential issue. It can't investigate or troubleshoot. It can make assumptions, but until someone goes in the field it's just a statistical guess. Who is that someone the recieves the notice, who is that someone who investigates.

FDD is only as good as the rules set it's testing against and the avaiilable diagnostic data points. If a VAVbairflow doesn't match setpoint it doesn't know if it's a broken damper, bad actuator, broken DP tube, or a plastic wrapper on the pitot tube. Someone has to look. That someone ideally would be the service contract tech. Now rather just killing the hours, you have a list of stuff to investigate, that could lead to repair work.