Not every career field gets the "sweeten the pot". Not only that, but people forget what I keep saying "the devil is in the details"... PCS, take TA, take promotions, take bonuses and they GOT YOU.
Also, for those who take flying it is not 4-5 yrs, it is 10!
I can't count on my hands and feet, plus, my BFFs hands and feet how many officers I know who couldn't jump at 4,5 or even 10. I think if I calculated how many who could jump when their ROTC or UPT commitment was over in the 21 yrs Bullet served it was 2 or 3. They had to stay on because they took TA or PCS or a promotion.
People believe it is so easy to leave, but in reality, at least for the AF it isn't.
Joe Schmoe gets commissioned AD in May 2011.
He attends SP school in Dec. 2011. Graduates in March 2012...clock starts ticking Dec 2011 for the 4 yrs.
March 2012 he is assigned to Eglin for 3 yrs. While there he decided to get his Masters using TA, and the last time he applied was Sept 2013. He now must pay back until Sept 2016.
His assignment at Eglin ends at Mar 2015, so he accepts an assignment to Germany for 3 yrs because he owes 18 months. Now he is stuck in Germany...try getting a job in the US! So to PCS back he accepts a new assignment with a payback...this is 2018. Even with a 2 yr commitment he is at 2020...which now puts him up for O4. He is married, has kids, car pmts and a mtg, hard thing to walk away from a sure paycheck when you have that hanging over your cranium.
The reality is the scholarship is the way to hook people because life has a funny way of getting into the way.