Enjoyable movie but full of plot holes and lacking explanation

Rating: 7/10 (30 July 2013)

I was really looking forward to this movie, i watched it, enjoyed it but I feel the movie is lacking.
First of all nowhere in the movie it is actually explained why the big alien is extracting resources from planets, it just makes no sense. Somehow it just decided to go to earth and start draining all the minerals. Also if jack is one of the clean up party shouldn't there be a bell ringing when there is literally no one else around who he even has contact with besides Julia? Also why would an alien obviously this powerful need humans to win a war for it and risk them somehow turning against them, just for repairing the bots? Would have seemed a lot more logical to just send in tens of thousands robots to win the war.
I also felt that too little was explained about what the entity/alien really is. Also it felt a bit cheap that the entire war was explained by Morgan Freeman in a small monologue.
Don't get me wrong, its a good movie. The special effects are great, the sound is great and I kind of liked the lonely/unreal feel of it but the story just felt really lacking. The movie has left me with a lot of questions, and not in a good way.