But if your transaction fee is set to zero, no miner will pick it up, right?
If you increase it, it would also increase the speed, at which, your transaction would be processed.
Now, how does that help the person, from a 3rd world country, paying in his currency, which is much weaker, than say the USD $.
The guy in USA pays e.g. 0,0007631 / 50 cents US and think it is fair, but the guy in the 3rd world country, pays for example in Argentine Peso and pay 4,064 peso.
The guy in the US cannot buy a hamburger with his 50 cents, but the guy in Argentina, can buy 2 hamburgers with that, so for him it's expensive to pay 0,0007631
to get his transaction processed.
It would not be a viable option for poor countries to accept it as a payment method.
What am I missing?
When we are talking about transferring fiat value, this is not necessarily true. Imagine sending a micro payment for $.65, or 0.001 BTC. With a standard input, you would have to pay a 10% fee in order to move that money. That is quite a high percentage.