As an AWAC pilot I see how Trip & Duty Rigs work on a regular basis and all I can say is that I'm extremely grateful we have them.

Firstly, they force the company to build more efficient trips because they can't have you sitting around for free.

And secondly, if you don't think they're worth having, have a look at some of your more screwed up trips (MX delays, CX'd flights, etc) and then apply the 2:1 Duty Rig or the 4:1 Trip Rig. Starts adding up very nicely.