A couple of reasons. Because the hp and torque is so extreme the tune has to run fairly rich, as a consequence I find that I keep fouling the spark plugs (three times in about 2 years). With that much power I'm always nervous of doing something foolish which is very easy to do. I have to consciously remind myself of which set of tires I'm running on (a set sticky DR's (00 wear rating) for fun close to home in good weather or a set of hard (500 wear rated) for long distance/ rain/light snow) which have very different traction/handling abilities. I can't find a set of mufflers that sound good with the LT headers and high-flow cats and dearly miss the sound of my old KR's on stock cats and exhaust manifolds. I also question the long term effect of so much power on my engine/drivetrain/chassis even though I don't use the power all that much. Which begs the question why do I need that much power in the first. I believe it was Thunder who said something to the affect that getting to learn how to handle what you've got is better then outright power.
In short, it's just a little too much for me. Some may say I'm wimping out or getting old (which is true). I've had my fun and I've got the dyno sheet to prove it, in the words of Clint Eastwood in on of his films "A man's got to know his limitations" I've reached and exceeded mine now it's time to clam it down.
There are other reasons but the one I've stated above are the major ones.
Again if I should decide to go for more power, a simple CA intake, pulley and tune on my stock blower will suffice.
I've yet to decide what I'll do the parts I take off, I'll worry about that in the future.