Never understood the whole "I feel like I'm trapped in the wrong gender/sex" argument.
How would you know what it feels like to be the other gender/sex?
I agree with you. I've wondered this myself. Having said this, if adults want to change their gender and they can afford it, that's their prerogative.
1 or 2 in 100 people are born intersex. Some would argue that it would be easier for them physically choose one sex or the other before they mature physically. Because they would still be minors, it is a decision the parents face under the advice of their doctor(s).
In the book Middlesex by Jeffrey Eugenides, the principal character,Cal Stephanides, who was born intersex chooses to remain as they were born, despite their parents and the doctor's recommendation to preform definitive surgery. In order to do so they are forced to make a decision to run away from home. This book is supposedly based on a true story.