Explain this

If tweeters should be ear level, why is it 3-way floorstanders never have the tweeters that high? Clever, huh?
umm.... cus most people are sitting when listening.
You can adjust the beam of which your tweeters fire by adjusting the rake angle of each speaker. This is an often overlooked and critical apect of speaker placement. This has been a subject here on the Gon as well as other forums. Go here: Iron Chef Speaker Setup
Boy I hope you didnt waste too much time trying to figure this out, nobody is the same height so there is room for adjustment as others have noted.
I think it's a good question, and many smaller floor standing speakers will sound better with stands, or even tilted back, for the average chair-sitter.

I remember hearing some Watt/Puppies at a delaer in a reasonably near-field listening set up and finding the soundstage unlistenably miniaturized due to my sitting height being too high for the speakers. I can't believe that they sold many of these like this.

I think many floor-standers sound too small in the average set up. When I got my first pair of line arrays, one of my first thoughts was, 'That's how an orchestra should sound.' It was magnificent. The stage was large, wide and deep, and particularly, at or above my level. Tastes are different, but I could never be happy with a shrunken stage.