I think one of the reasons is that because more and more people do it, it becomes more morally "acceptable" to do so.
Another reason could be that people see it more as a monetary contract. If a company overseas willing to pay the monetary penalty of breaking a bond offers to hire the scholar after his/her education, most people would definitely take the opportunity of enjoying a higher pay and the prestige that comes with it, as opposed to coming back to work in Singapore.
One other reason which I believe to encourage this, is the government's habit of imposing hefty fines to enforce laws. The unfortunate side effect of this is that it breeds the mindset in people that any contract with the government is purely monetary. The unconcious thought process for most people when they break the speed limit, is that its bad not because its wrong and dangerous, but because they would have to pay a heavy fine. Same way, when someone break his/her bond, its bad not because its (supposedly) morally wrong, but because he/she would have to pay the expensive penalty. So when there's an opportunity to circumvent the monetary disincentive of breaking a bond, the scholar would most probably grasp it.
As for people who can afford to pay for their own overseas, but choose to accept a bond with the intent of breaking it as they would be able to pay off the penalty, it is probably due to the "prestige" of studying overseas on a scholarship, since money isn't a factor to them. A reason for this would be pure selfishness, nothing more.
That's all I can think of at the moment. Let me know if it helps
