Everyone I know went to see Transformers 2 but only a few of them liked it. It's one of those movies that everyone went to see to have an opinion.
I admit to being one of those people. Yes, I know I should've known better, having seen the first movie, but I couldn't help myself. I'm part of the blame. I wanted to see if the movie was really as racist as people were saying it was.
Plus I used to like Transformers when I was a kid, so there was some sentimentality that influenced my decision to to go see it. Ultimately, I wasn't going to not see it. I forgot to remind myself it's not 1985 anymore.
EDIT: And, yeah, if children are flocking to see a Transformers movie, then it's not just them. You've got one or both parents coming along and their siblings. In children's movies (of which TF2 is a bad example), for every one child who wants to see it, you're selling 2-5 tickets. How many of the parents would've really gone to see Transformers 2 on their own without the kids?