Why not? I can't do something that's different and must do what everyone else already has?
I enjoy trying to attempt case builds and do setups that people have not attempted. After seeing only a handful of truly "custom" tj08 builds here I thought people may appreciate seeing something different from the norm.
I replaced the front fan because I wanted something that would be very quiet yet still move a decent amount of air. I'm trying to go for as quiet of a build as I can while also achieving great temps for all components.
Yes the H80 does fit entirely inside the case but that's not where I wanted it for a couple reasons. First was that I like having the inside of the case as clean as possible. With the H80 inside it takes up a lot of room and I don't like the way that looks at all. Also when running it in push/pull it only clears the waterblock by a couple millimeters. If you want to add a fan shroud to the mix then forget about it. You will either have to shave down the one side of the fan and deal with it covering the nice looking waterblock entirely.
Also with the H80 internal you are covering up some motherboard components that tend to get nice and warm. With them being covered up they are not getting much airflow.
With the H80 externally mounted it removes the rad from the higher air temp inside of the case. All motherboard components are getting nice airflow because they are not completely covered up by 2 fans and a rad, and I am able to easily run a fan shroud on the single fan mounted inside of the case without it running the looks of the interior.