My opinion on this is that these types of people have always been around but it is becoming more common. There are multiple factors playing into it.
Men do tend to be somewhat different than woman on average when it comes to our biological influences on behavior with sex. Men are slightly more casual because women have a heavy biological price to pay for picking a poor mate, so they are slightly more selective. This alone does not explain it.
Primarily one of the problems with third world countries that you bring up is that the increasing combination of poverty and lack of resources to go around and overpopulation lead to a break down of community and love and respect for one another. Try getting around in a country like India or Mexico without having to grease and bribe a few people. When we lack basic resources to fulfill our Maslow needs then we don’t achieve self actualization which then means we lose community. We lose God because we lost community.
We look at others in society as resources to be used. We lack money in an overpopulated society we turn into scammed. We lack sexual satisfaction when surrounded by many beautiful people then we look at beautiful sexual people as things to be used.
Women do it too but other societal influences cause them to be a little different about it generally. There is still the slut shaming aspect that teaches women it is not acceptable to use men sexually but it is acceptable to be used sexually. Many women are groomed and convinced that it is good to be used by a sleazebag.
But that’s the thing about using other people for sex, money, power, emotional validation, all of the above, you can’t play thst game and not also be used up by others. Everybody loses that game, your soul withers and dies.