I didn't say anything about what causes Bangladesh's economic problems. I used Bangladesh as an example because it's a particularly stark illustration of the social costs of unaddressed poverty. Speaking from first-hand experience: it's a place where you can be rich, live in the most exclusive enclave in the capital city, yet still be panhandled by orphan kids with missing hands when you walk out your door. There's a dollar value you can place on alleviating that state of affairs, even based on purely selfish reasons like your own quality of life. The problem with private charities is that, for very basic economic reasons, they cannot be expected to fully capture the dollar value of alleviating poverty in the society.
Therefore I have the right to hire a bodyguard to use force in my defense. (In fact it is the same right - delegated.)
Therefore we have the right to elect a sheriff to use force in our defense.
...But I do NOT have the right to beat and rob people.
Therefore, neither do I have any right to hire a bodyguard to beat and rob people.
Therefore, neither does our sheriff have any right to beat and rob people -- even if we voted for him to do so! Because you cannot delegate powers you never had.
Therefore the question isn't whether society should provide social welfare for the needy. Rather, the question is whether we have a moral right to use VIOLENCE to FORCE people to provide social welfare for the needy. (We don't.)
The reason you see poverty in various nations is because they do not have economic freedom and secure property rights. The nations with the worst poverty are the ones with the worst protections of rights. The nations with the lowest poverty are the nations with the best protections of rights. And note: those are also the nations who donate the most money to charity.
Government can never fix poverty by using violence to forcefully redistribute wealth. All that will do is cause worse poverty.
The best a government can do is strongly protect rights and economic freedoms -- then you will have a rich nation, which will not have poverty problems in the first place, and which will easily be able to cover the rest through private charity.
Unfortunately we do not see any governments today that respect rights and freedoms in this way, although some are better than others. But proposed solutions based on "social welfare" will only make those problems worse, not better.