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


...when most peoples ears are much lower when seated??

I've read many times that the tweeter should be at approximately ear level.  Well, I am 6 feet tall, and sitting straight up on my couch my ears are about 40 inches off the floor, lower of course if slouch.  My Artemis - Eos speakers have the tweeters at 45 inches high, so not too bad, but many others that I've seen are 50 inches high and more and I don't understand the designer's thinking.   Is a 10 - 12 inch difference in height acceptable or should the speaker be tilted down, which I think would create a whole new set of issues.
aigenga
Late to the discussion here. I took a look at your fine setup. Very nice.

Your room doesn't look like it wouldn't  work, but have you ever tried the Cardas setup?
http://www.cardas.com/room_setup_calculators.php YMMV

Not a wife approved setup, but the possible sonics...!

I recently did mine per calculator, and I'm able to resist a decadent speaker upgrade. Mine are about 5.5' out and 3.5 from the side walls, toed to intersect just behind my ears. 6ft apart(woofer ctr-ctr) and couch about 6-7'. When I do a listening session, I use bass traps and first reflection panels-instant listening room sonics.

My setup is in a living area(13x26) and not a dedicated room.

Oh finally somebody using math to setup a room

next run your curves....
easy to do
Vandertones and an SPL meter

knowing the truth enables the cat to make progress vs chase tail

Related issue. My soundstage is centered slightly below ear level, as is the midpoint between tweeter and mid. I'd like to raise it, so I tilted the speakers back slightly. That seems to make it even lower. Make sense?
Is my brain back projecting the upward facing wave "vectors" to a lower point of origin?
There trying to match where you're ears are. 
  Are your ears bigger then
4  in's long ?  You might have to get stuffing in the sofa.   
The tweeters on my Focal 936's are something like 39 inches high. I barely notice and difference if I try to sit tall and ear level with them, but standing makes a noticable difference. I can't believe I'm going to say this, but I'm actually going to agree with geoffkait in that being ear level with the midrange drivers does seem to contribute to their dynamic impact.