Because that is what is expected of you. The "career path" of a born- in who is under a microscope generally leans towards pioneering out of high school, becoming a MS at 19-20, kissing butt for 6-8 years and then appointment as an elder. Don't underestimate the pressure that is put upon these young men. The congregation and Circuit overseers will groom and encourage young servants to reach out to be elders. I think that the intense pressure comes from the congregations desire to see a "success" come out from the young ones in the hall. Most kids split after they are out of school. This puts more pressure on the ones who stay to become the superstars that their peers weren't.
I know for myself, I didn't want authority, power, and prestige as an elder. I just wanted approval and acceptance from the people that I had known my entire life.
SIAM