Sometimes people don't go to hear every single song from a new album - they go to hear the band. Old songs are obviously part of the back catalogue so there is no reason why they would not expect to hear an old number or 2, unless it is advertised as being the "insert album name here" tour. Even then, most bands encore with an older, popular number.
"Pandering to fans" - really? Those fans made you who you are by supporting your music - how about giving a little back as well and letting them feel part of the gig. So what if a bit of singing/dancing/clapping/stomping along is cheesy - it's about the music, the experience, the excitement and if that's offensive to you, what's the point?
No wonder people walk away from hearing big bands saying it wasn't as good as they were expecting it to be. No wonder people would rather sit home and watch X-factor/Idol/The voice etc!