Well, there's a whole bunch of other stuff too. Most of the time with animal models, we induce cancer by a variety of means - examples include using breeds with certain cancer suppressing genes knocked out, heavy exposure to carcinogens, or direct grafting/injection. These are all mechanisms of getting cancer that are extremely atypical in the human beings we are trying to cure, which may (I think its super likely, especially in the case of knockout genes and grafting) influence cancer-treatment interaction.

Exactly. I know of no mouse study that actually tries to replicate what we want to do in humans.

In regards looking for a cure for cancer we are like the drunk who lost their keys in the dark alleyway, but who is searching around the street lamp since the light is better. Until we actually start doing the right studies we will really struggle getting anywhere.