Why make things over complicated?

I watched a film called 'Sucker Punch' last night... but I didn't get it? I tried my best to understand why the film seemed to move between realism and fantasy. Was it because the girls in the film wanted to escape the reality and so created this fantasy world to try and conquer that or have I missed the plot completely?

I think it is easy to make something over complicated and become too far from belief. I personally as a photographer and film enthusiast prefer my films and images to be something that tackles reality. I am not someone who would enjoy a sci-fi film or something similar; so perhaps this is the reason why I do not understand it. However; maybe it is my lack of optimism for these films which prevents me from opening up and taking them for what they are?

All I know is that; if someone wants to shed some light on the plot, then I would be more than happy to listen.