Why are tweeters so high off of the ground in many tower speakers...

Thanks to all for their input.  My question was more general than one that concerns my set-up.

I referenced my speakers as a starting-point for the discussion rather than a plea for help.  But, since many respondents have taken the time to address these speakers let me say thanks and fill in some details.  The speakers and I sit in an equilateral triangle nine feet on each side, and they point directly at my ears.  My room prevents me from going back another foot or two, which I think would be beneficial.  I am very happy with the performance of these speakers in my rig, very rarely do I hear anything better.  I use four monoblock amps: Jolida 211 Fusion tube amps on top, and Wyred For Sound mAmps on the for the bass boxes; crossover is at 70 hz.  

I asked the question because I see so many tower speakers where the tweeter is at the top, not close to average ear level.  Perhaps this is because of the "loudness wars" and crazy emphasis of top and bottom in a lot of pop music today.  My own listening doesn't include this type of music and so I wonder how these speakers would do on classical and jazz and acoustical music in general?  I think that they would need a listening distance of twelve feet or more before the tweeter would cohere to the sound.  Any Revel Salon owners out there care to comment.

I experimented by bringing my couch up five inches to bring my ears to tweeter height.  The result was like I was looking down on the stage from the cheap seats.  Horrible, I quickly went back to my current seating height.  To achieve the thirty inches that Atkinson recommends I would have to sit on a thin pad on the floor and that ain't me.  
But it does make clear that the maxim that tweeters should be at ear-level is far from universal. It is well worth the effort to try different seat heights - yet another room adjustment that makes all of the difference and that so many of us ignore.

2channel8, I would raise the speakers or lower your chair.  I got that same result when I tried raising my couch five inches.  I will be trying again but only by two inches.