That is beyond despicable. Those people should be barred from entry to prevent them from doing this. Unfortunately, with the current state of Nepal, I doubt they're capable of effective immigration control. Even so, these monsters would find prey among the vulnerable women there.
The problem is that the local politicians are also corrupt. They get commissions from these traffickers. Also, Indian citizens are allowed to enter Nepal without a visa.
The government can't change this, because many hundreds of thousands of Nepalese workers eke out a living in India. Ah, it always boils down to politicians getting in the action. Would not be surprised if they will eventually found actively supplying girls to these traffickers.
About
this, are you saying that they can't require Indians visa because India might do something? Are these Nepalese workers also allowed into India without visa?
Yes. According to the border agreement, citizens of Nepal and Bhutan does not need a visa to enter India. They just need to show a government provided ID card at the border check post. The same is applicable to Indian citizens who visit either Nepal or Bhutan.