Why are the high notes on a saxophone hard?

I have been asked this question for over 50 years now and it is simple…. They aren’t! …. Playing the altissimo on the saxophone is just a matter of hearing the right note and learning how to produce that note….. everyone has their own idea of how to play the altissimo from closing the throat to opening the throat, tightening the embouchure to losing the embouchure…. And there are very good players that do both….
when you practice trying to learn the altissimo it is important to play the note in the lower register of the saxophone and then try to play the altissimo note…. We as players tend to get sharper as we play higher…. So by playing the lower note and trying to match the altissimo note to it….. you will be more likely to learn the altissimo note with better pitch….
*Keep in mind when you talk to a great saxophone player about the altissimo they may say things that will not work for you…. I have heard great players play the crap out of the altissimo, high as you can go, sounding very good with fingerings I could not come close to the notes they are playing…. listen then find out what works for you…..