An encore, by definition, is extra music, over and above the actual concert. If you don't get an encore, you aren't being shorted anything, you still got the concert. You just aren't getting anything extra.
DT has worked on this project for 2 years, and they decided that they would present it in its entirety, live, with this dedicated live presentation/videos/lighting/visuals. Everything they have done to prepare this live concert tour is this album. I understand completely why they wouldn't also want to throw out another unrelated song just to say they were doing it.
I understand completely that rock show convention is to have an encore, and why a general audience would expect one (or at least hope for one). But DT has stated that there won't be one on this tour, so whining about it now seems a little petty. I mean, you got over two hours of music, and you boo because you don't get that one extra song? Come on.