Replying to Dinosaurs, why eat us?

so im watching the end of jurassic park iii (and yes the two sequels absolutely pale compared to the original) and im wondering how come dinosaurs seem so extremely inclined to eat humans.  yes i know they are carnivorous and they eat meat in order to survive but still these things are going well out of their way to eat these people, and to my dismay they dont succeed as often as id like. 

i mean is it like how i will go out of my way to go through a puddle while im driving? can they just not help it?