Audio problem: When Steve Martin is talking to Bonnie Hunt on the phone and the kids are playing, a small dart lands between his feet. The sound the dart makes when it sticks to the floor is not accurate at all and deliberately sounds as if it comes from a object much heavier. (00:50:25)
Audio problem: When Dylan is over at the Baker's new house, Jake says "You're gonna wanna stop now dude" but when he says this, the movement of his mouth isn't matching the words he's saying. (00:23:40)
Audio problem: When Sarah Baker says "I would feel happier and stronger if we vote on it", he lips move way too quickly for the words to catch up.
Answer: It seems that the fact the family can't take care of themselves is added to part of the humour of the film. 12 children is a lot, and think about all those rows and all that mess.
Hamster ★
It's not like they couldn't take care of themselves. As shown with the breakfast scene at the beginning, they seem to function pretty well when they all get along. Tom and Kate were just usually home more frequently than some other parents. It also didn't help that it was the first time that one of the parents was gone for an extended period and the parent that was left home (Tom) had never had to deal with all the kids on his own. Also, the only time we see complete chaos in the house is the first day that Kate has been gone. After that the kids are more behaved (at home).