Oddly enough I like going to live shows for both. The band can still sing all the parts and still have crowd interaction.
And yes, live shows are kind of about live music. That includes singing. So yes. I do go to hear the band play. Whether it is like the record or an alternate version is not relevant.
Either way, I pay to hear the band play and sing. I could not care less about what the rest of the crowd says/sings during a show.
Well, from Alex's perspective, it's fuckin' awesome when you're on stage and get the crowd to sing back the lyrics to your song. Plus, it's usually fun for the crowd too. So i'm not really sure what you are complaining about. Shows are just a good time.