This may be little bit off the issue mentioned above but , heres my take.. 

Few people still leave usa even after having papers and better jobs and one cant call them retards. They might want to be closer to their family, raise kids on their own and not by baby sitters. Like in earlier posts, In US, you will achieve material wellbeing, but people still may not be happy . Family members back home etcs and even though he/she could bring them back, it may not feel as in Nepal. People might want to raise their kids in nepalese society, teach nepalese values, traditions  etc....After living here for a long time, ppl get used to comforts such as no blackouts,better roads..law and order and many more, If someone is from relatively wealthy family in Nepal, they could be happy there. If someone just gets here from village and has nothing left out in Nepal and also has not succeeded in US, he/she will not dare going back to Nepal or anywhere else.

In Nepal, there is bandh and no law and order. But still almost 30 million ppl are surviving and many are making lot more money then ppl here in the US on student visas or working professionals. They have more time for their family and have houses, need not worry about mortgages ...