what be the answer to this 'phenomenon'

One cannot help but, wonder... A natural existence of something within each person that some have the courage to acknowledge. 
Many a time it is difficult to have a definitive answer when it comes to questions involving the human psyche. 
Would this be due to the fact that each human has that one chromosome, out of billions, its combination with another, that makes one unique to anybody else. So reactions, behaviour and much more, that define one, can be standard to a point, and then begin to branch out in different ways as the matter at hand becomes more intricate.
And so, looking at how humans deal with matters of the body paired with their mind. 
Why is it that ones sensuality or sexuality is a topic that raises feelings of discomfort. And when spoken about, it tends to be in a light negative raising heated debate , making most cower into dark corners for fear of being pointed out as some kind of delinquent sexual predator or abuser or sexual psycho.
Like anything in life, there are bad apples, and that age old battle of choice between good and bad will be with us eternal. But, should one not believe that the intelligent educated civilised wise experienced logic humans love to associate themselves with,  should prevail and set free the need to express and accept that sexual and sensual chromosome, i would imagine, every human being is born with.
Why is it, as one gets older one tends to shy away from acknowledging ones sensual and sexual drive. 
What is it that where, once in youth one openly laughed and dabbled in kisses passionate, touch soft, lovemaking sweaty and lasting for hours, fucking like bunnies, quickies, oral and much more...yet, age wants one to deny the existence of enjoyment of what youth so readily accepted.
One could go on forever as to all the possibilities.... what do u think be the reason for this 'phenomenon'? 
Is maturity and age a cruel thief of something so beautiful all humans were given the pleasure of knowing and enjoying...sensuality and sexuality...?


RB.