If the company is doing this, then you have to ask why ?? The answer is probably because of the attrition rate . So, the answer, to try and force people, financially to stay for at least 3 years.
Many people come here and say, I can do 5yrs, 10 yrs, get my command etc, only after living here for a year to say this isn't for me !
As, most people have never been here before, you will not know how you feel until you have lived here for a while, in that case, would you take a chance on this type of bond package ??
In fact it may encourage people to decide to jump ship sooner...